Re: [PATCH] erofs: support adjust lz4 history window size
On Tue, Feb 23, 2021 at 10:03:59AM +0800, Huang Jianan wrote:
> Hi Xiang,
>
> On 2021/2/22 12:44, Gao Xiang wrote:
> > Hi Jianan,
> >
> > On Thu, Feb 18, 2021 at 08:00:49PM +0800, Huang Jianan via Linux-erofs
> > wrote:
> > > From: huangjianan
> > >
> > > lz4 uses LZ4_DISTANCE_MAX to record history preservation. When
> > > using rolling decompression, a block with a higher compression
> > > ratio will cause a larger memory allocation (up to 64k). It may
> > > cause a large resource burden in extreme cases on devices with
> > > small memory and a large number of concurrent IOs. So appropriately
> > > reducing this value can improve performance.
> > >
> > > Decreasing this value will reduce the compression ratio (except
> > > when input_size > > currently only supports 4k output, reducing this value will not
> > > significantly reduce the compression benefits.
> > >
> > > Signed-off-by: Huang Jianan
> > > Signed-off-by: Guo Weichao
> > > ---
> > > fs/erofs/decompressor.c | 13 +
> > > fs/erofs/erofs_fs.h | 3 ++-
> > > fs/erofs/internal.h | 3 +++
> > > fs/erofs/super.c| 3 +++
> > > 4 files changed, 17 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> > > index 1cb1ffd10569..94ae56b3ff71 100644
> > > --- a/fs/erofs/decompressor.c
> > > +++ b/fs/erofs/decompressor.c
> > > @@ -36,22 +36,27 @@ static int z_erofs_lz4_prepare_destpages(struct
> > > z_erofs_decompress_req *rq,
> > > struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
> > > unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
> > > BITS_PER_LONG)] = { 0 };
> > > + unsigned int lz4_distance_pages = LZ4_MAX_DISTANCE_PAGES;
> > > void *kaddr = NULL;
> > > unsigned int i, j, top;
> > > + if (EROFS_SB(rq->sb)->compr_alg)
> > > + lz4_distance_pages = DIV_ROUND_UP(EROFS_SB(rq->sb)->compr_alg,
> > > + PAGE_SIZE) + 1;
> > > +
> > Thanks for your patch, I agree that will reduce runtime memory
> > footpoint. and keep max sliding window ondisk in bytes (rather
> > than in blocks) is better., but could we calculate lz4_distance_pages
> > ahead when reading super_block?
> Thanks for suggestion, i will update it soon.
> > Also, in the next cycle, I'd like to introduce a bitmap for available
> > algorithms (maximum 16-bit) for the next LZMA algorithm, and for each
> > available algorithm introduces an on-disk variable-array like below:
> > bitmap(16-bit)2 1 0
> > ... LZMALZ4
> > __le16 compr_opt_off; /* get the opt array start offset
> > (I think also in 4-byte) */
> >
> > compr alg 0 (lz4) __le16 alg_opt_size;
> > /* next opt off = roundup(off + alg_opt_size, 4); */
> > __le16 lz4_max_distance;
> >
> > /* 4-byte aligned */
> > compr alg x (if available) u8 alg_opt_size;
> > ...
> >
> > ...
> >
> > When reading sb, first, it scans the whole bitmap, and get all the
> > available algorithms in the image at once. And then read such compr
> > opts one-by-one.
> >
> > Do you have some interest and extra time to implement it? :) That
> > makes me work less since I'm debugging mbpcluster compression now...
>
> Sounds good, I will try to do this part of the work.
Yeah, but it seems to be part of the next LZMA algorithm patchset (with
a new brand new INCOMPET feature). I think we could introduce a __le16
lz4_max_distance field from sb reserved for now as a simple backporting
solution (since we only use < 64kb sliding window, so the image would
be forward compatibility with old kernels. 0 means 64kb sliding window,
otherwise it will < 64kb.)
And with the new INCOMPAT_COMPR_OPT feature, lz4_max_distance field
will be turned into compr_opt_off instead. And variable-array will be
used then.
So could you revise the patchset as above? Thanks!
Thanks,
Gao Xiang
>
> Thanks,
>
> Jianan
>
> > Thanks,
> > Gao Xiang
> >
>
Re: [PATCH] erofs: support adjust lz4 history window size
Hi Xiang,
On 2021/2/22 12:44, Gao Xiang wrote:
Hi Jianan,
On Thu, Feb 18, 2021 at 08:00:49PM +0800, Huang Jianan via Linux-erofs wrote:
From: huangjianan
lz4 uses LZ4_DISTANCE_MAX to record history preservation. When
using rolling decompression, a block with a higher compression
ratio will cause a larger memory allocation (up to 64k). It may
cause a large resource burden in extreme cases on devices with
small memory and a large number of concurrent IOs. So appropriately
reducing this value can improve performance.
Decreasing this value will reduce the compression ratio (except
when input_size
Signed-off-by: Guo Weichao
---
fs/erofs/decompressor.c | 13 +
fs/erofs/erofs_fs.h | 3 ++-
fs/erofs/internal.h | 3 +++
fs/erofs/super.c| 3 +++
4 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 1cb1ffd10569..94ae56b3ff71 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -36,22 +36,27 @@ static int z_erofs_lz4_prepare_destpages(struct
z_erofs_decompress_req *rq,
struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
BITS_PER_LONG)] = { 0 };
+ unsigned int lz4_distance_pages = LZ4_MAX_DISTANCE_PAGES;
void *kaddr = NULL;
unsigned int i, j, top;
+ if (EROFS_SB(rq->sb)->compr_alg)
+ lz4_distance_pages = DIV_ROUND_UP(EROFS_SB(rq->sb)->compr_alg,
+ PAGE_SIZE) + 1;
+
Thanks for your patch, I agree that will reduce runtime memory
footpoint. and keep max sliding window ondisk in bytes (rather
than in blocks) is better., but could we calculate lz4_distance_pages
ahead when reading super_block?
Thanks for suggestion, i will update it soon.
Also, in the next cycle, I'd like to introduce a bitmap for available
algorithms (maximum 16-bit) for the next LZMA algorithm, and for each
available algorithm introduces an on-disk variable-array like below:
bitmap(16-bit)2 1 0
... LZMALZ4
__le16 compr_opt_off; /* get the opt array start offset
(I think also in 4-byte) */
compr alg 0 (lz4) __le16 alg_opt_size;
/* next opt off = roundup(off + alg_opt_size, 4); */
__le16 lz4_max_distance;
/* 4-byte aligned */
compr alg x (if available) u8 alg_opt_size;
...
...
When reading sb, first, it scans the whole bitmap, and get all the
available algorithms in the image at once. And then read such compr
opts one-by-one.
Do you have some interest and extra time to implement it? :) That
makes me work less since I'm debugging mbpcluster compression now...
Sounds good, I will try to do this part of the work.
Thanks,
Jianan
Thanks,
Gao Xiang
Re: [PATCH] erofs: support adjust lz4 history window size
Hi Jianan,
On Thu, Feb 18, 2021 at 08:00:49PM +0800, Huang Jianan via Linux-erofs wrote:
> From: huangjianan
>
> lz4 uses LZ4_DISTANCE_MAX to record history preservation. When
> using rolling decompression, a block with a higher compression
> ratio will cause a larger memory allocation (up to 64k). It may
> cause a large resource burden in extreme cases on devices with
> small memory and a large number of concurrent IOs. So appropriately
> reducing this value can improve performance.
>
> Decreasing this value will reduce the compression ratio (except
> when input_size currently only supports 4k output, reducing this value will not
> significantly reduce the compression benefits.
>
> Signed-off-by: Huang Jianan
> Signed-off-by: Guo Weichao
> ---
> fs/erofs/decompressor.c | 13 +
> fs/erofs/erofs_fs.h | 3 ++-
> fs/erofs/internal.h | 3 +++
> fs/erofs/super.c| 3 +++
> 4 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index 1cb1ffd10569..94ae56b3ff71 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -36,22 +36,27 @@ static int z_erofs_lz4_prepare_destpages(struct
> z_erofs_decompress_req *rq,
> struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
> unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
> BITS_PER_LONG)] = { 0 };
> + unsigned int lz4_distance_pages = LZ4_MAX_DISTANCE_PAGES;
> void *kaddr = NULL;
> unsigned int i, j, top;
>
> + if (EROFS_SB(rq->sb)->compr_alg)
> + lz4_distance_pages = DIV_ROUND_UP(EROFS_SB(rq->sb)->compr_alg,
> + PAGE_SIZE) + 1;
> +
Thanks for your patch, I agree that will reduce runtime memory
footpoint. and keep max sliding window ondisk in bytes (rather
than in blocks) is better., but could we calculate lz4_distance_pages
ahead when reading super_block?
Also, in the next cycle, I'd like to introduce a bitmap for available
algorithms (maximum 16-bit) for the next LZMA algorithm, and for each
available algorithm introduces an on-disk variable-array like below:
bitmap(16-bit)2 1 0
... LZMALZ4
__le16 compr_opt_off; /* get the opt array start offset
(I think also in 4-byte) */
compr alg 0 (lz4) __le16 alg_opt_size;
/* next opt off = roundup(off + alg_opt_size, 4); */
__le16 lz4_max_distance;
/* 4-byte aligned */
compr alg x (if available) u8 alg_opt_size;
...
...
When reading sb, first, it scans the whole bitmap, and get all the
available algorithms in the image at once. And then read such compr
opts one-by-one.
Do you have some interest and extra time to implement it? :) That
makes me work less since I'm debugging mbpcluster compression now...
Thanks,
Gao Xiang
[PATCH] erofs: support adjust lz4 history window size
From: huangjianan
lz4 uses LZ4_DISTANCE_MAX to record history preservation. When
using rolling decompression, a block with a higher compression
ratio will cause a larger memory allocation (up to 64k). It may
cause a large resource burden in extreme cases on devices with
small memory and a large number of concurrent IOs. So appropriately
reducing this value can improve performance.
Decreasing this value will reduce the compression ratio (except
when input_size
Signed-off-by: Guo Weichao
---
fs/erofs/decompressor.c | 13 +
fs/erofs/erofs_fs.h | 3 ++-
fs/erofs/internal.h | 3 +++
fs/erofs/super.c| 3 +++
4 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 1cb1ffd10569..94ae56b3ff71 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -36,22 +36,27 @@ static int z_erofs_lz4_prepare_destpages(struct
z_erofs_decompress_req *rq,
struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
BITS_PER_LONG)] = { 0 };
+ unsigned int lz4_distance_pages = LZ4_MAX_DISTANCE_PAGES;
void *kaddr = NULL;
unsigned int i, j, top;
+ if (EROFS_SB(rq->sb)->compr_alg)
+ lz4_distance_pages = DIV_ROUND_UP(EROFS_SB(rq->sb)->compr_alg,
+ PAGE_SIZE) + 1;
+
top = 0;
for (i = j = 0; i < nr; ++i, ++j) {
struct page *const page = rq->out[i];
struct page *victim;
- if (j >= LZ4_MAX_DISTANCE_PAGES)
+ if (j >= lz4_distance_pages)
j = 0;
/* 'valid' bounced can only be tested after a complete round */
if (test_bit(j, bounced)) {
- DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
- DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
- availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
+ DBG_BUGON(i < lz4_distance_pages);
+ DBG_BUGON(top >= lz4_distance_pages);
+ availables[top++] = rq->out[i - lz4_distance_pages];
}
if (page) {
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 9ad1615f4474..bffc02991f5a 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -39,7 +39,8 @@ struct erofs_super_block {
__u8 uuid[16]; /* 128-bit uuid for volume */
__u8 volume_name[16]; /* volume name */
__le32 feature_incompat;
- __u8 reserved2[44];
+ __le16 compr_alg; /* compression algorithm specific parameters */
+ __u8 reserved2[42];
};
/*
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 67a7ec945686..f1c99dc2659f 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -70,6 +70,9 @@ struct erofs_sb_info {
/* pseudo inode to manage cached pages */
struct inode *managed_cache;
+
+ /* compression algorithm specific parameters */
+ u16 compr_alg;
#endif /* CONFIG_EROFS_FS_ZIP */
u32 blocks;
u32 meta_blkaddr;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index d5a6b9b888a5..198435e3eb2d 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -174,6 +174,9 @@ static int erofs_read_superblock(struct super_block *sb)
sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact));
sbi->root_nid = le16_to_cpu(dsb->root_nid);
sbi->inos = le64_to_cpu(dsb->inos);
+#ifdef CONFIG_EROFS_FS_ZIP
+ sbi->compr_alg = le16_to_cpu(dsb->compr_alg);
+#endif
sbi->build_time = le64_to_cpu(dsb->build_time);
sbi->build_time_nsec = le32_to_cpu(dsb->build_time_nsec);
--
2.25.1
