On Mon, May 20, 2019 at 11:28:01AM +0200, Michal Hocko wrote: > [cc linux-api] > > On Mon 20-05-19 12:52:54, Minchan Kim wrote: > > System could have much faster swap device like zRAM. In that case, swapping > > is extremely cheaper than file-IO on the low-end storage. > > In this configuration, userspace could handle different strategy for each > > kinds of vma. IOW, they want to reclaim anonymous pages by MADV_COLD > > while it keeps file-backed pages in inactive LRU by MADV_COOL because > > file IO is more expensive in this case so want to keep them in memory > > until memory pressure happens. > > > > To support such strategy easier, this patch introduces > > MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER options in madvise(2) like > > that /proc/<pid>/clear_refs already has supported same filters. > > They are filters could be Ored with other existing hints using top two bits > > of (int behavior). > > madvise operates on top of ranges and it is quite trivial to do the > filtering from the userspace so why do we need any additional filtering? > > > Once either of them is set, the hint could affect only the interested vma > > either anonymous or file-backed. > > > > With that, user could call a process_madvise syscall simply with a entire > > range(0x0 - 0xFFFFFFFFFFFFFFFF) but either of MADV_ANONYMOUS_FILTER and > > MADV_FILE_FILTER so there is no need to call the syscall range by range. > > OK, so here is the reason you want that. The immediate question is why > cannot the monitor do the filtering from the userspace. Slightly more > work, all right, but less of an API to expose and that itself is a > strong argument against.
What I should do if we don't have such filter option is to enumerate all of vma via /proc/<pid>/maps and then parse every ranges and inode from string, which would be painful for 2000+ vmas. > > > * from v1r2 > > * use consistent check with clear_refs to identify anon/file vma - surenb > > > > * from v1r1 > > * use naming "filter" for new madvise option - dancol > > > > Signed-off-by: Minchan Kim <minc...@kernel.org> > > --- > > include/uapi/asm-generic/mman-common.h | 5 +++++ > > mm/madvise.c | 14 ++++++++++++++ > > 2 files changed, 19 insertions(+) > > > > diff --git a/include/uapi/asm-generic/mman-common.h > > b/include/uapi/asm-generic/mman-common.h > > index b8e230de84a6..be59a1b90284 100644 > > --- a/include/uapi/asm-generic/mman-common.h > > +++ b/include/uapi/asm-generic/mman-common.h > > @@ -66,6 +66,11 @@ > > #define MADV_WIPEONFORK 18 /* Zero memory on fork, child only */ > > #define MADV_KEEPONFORK 19 /* Undo MADV_WIPEONFORK */ > > > > +#define MADV_BEHAVIOR_MASK (~(MADV_ANONYMOUS_FILTER|MADV_FILE_FILTER)) > > + > > +#define MADV_ANONYMOUS_FILTER (1<<31) /* works for only anonymous vma > > */ > > +#define MADV_FILE_FILTER (1<<30) /* works for only file-backed vma */ > > + > > /* compatibility flags */ > > #define MAP_FILE 0 > > > > diff --git a/mm/madvise.c b/mm/madvise.c > > index f4f569dac2bd..116131243540 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -1002,7 +1002,15 @@ static int madvise_core(struct task_struct *tsk, > > unsigned long start, > > int write; > > size_t len; > > struct blk_plug plug; > > + bool anon_only, file_only; > > > > + anon_only = behavior & MADV_ANONYMOUS_FILTER; > > + file_only = behavior & MADV_FILE_FILTER; > > + > > + if (anon_only && file_only) > > + return error; > > + > > + behavior = behavior & MADV_BEHAVIOR_MASK; > > if (!madvise_behavior_valid(behavior)) > > return error; > > > > @@ -1067,12 +1075,18 @@ static int madvise_core(struct task_struct *tsk, > > unsigned long start, > > if (end < tmp) > > tmp = end; > > > > + if (anon_only && vma->vm_file) > > + goto next; > > + if (file_only && !vma->vm_file) > > + goto next; > > + > > /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ > > error = madvise_vma(tsk, vma, &prev, start, tmp, > > behavior, &pages); > > if (error) > > goto out; > > *nr_pages += pages; > > +next: > > start = tmp; > > if (prev && start < prev->vm_end) > > start = prev->vm_end; > > -- > > 2.21.0.1020.gf2820cf01a-goog > > > > -- > Michal Hocko > SUSE Labs
