On Wed, Nov 04, 2020 at 07:27:03AM +0800, Minchan Kim wrote:
> Sorry if this mail corrupts the mail thread or had heavy mangling
> since I lost this mail from my mailbox so I am sending this mail by
> web gmail.
>
> On Thu, Oct 22, 2020 at 10:18 AM <vji...@codeaurora.org> wrote:
> >
> > From: Yogesh Lal <y...@codeaurora.org>
> >
> > Use STACK_HASH_ORDER_SHIFT to configure STACK_HASH_SIZE.
> >
> > Aim is to have configurable value for STACK_HASH_SIZE,
> > so depend on use case one can configure it.
> >
> > One example is of Page Owner, default value of
> > STACK_HASH_SIZE lead stack depot to consume 8MB of static memory.
> > Making it configurable and use lower value helps to enable features like
> > CONFIG_PAGE_OWNER without any significant overhead.
> >
> > Signed-off-by: Yogesh Lal <y...@codeaurora.org>
> > Signed-off-by: Vinayak Menon <vinme...@codeaurora.org>
> > Signed-off-by: Vijayanand Jitta <vji...@codeaurora.org>
> > ---
> > lib/Kconfig | 9 +++++++++
> > lib/stackdepot.c | 3 +--
> > 2 files changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/Kconfig b/lib/Kconfig
> > index 18d76b6..b3f8259 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -651,6 +651,15 @@ config STACKDEPOT
> > bool
> > select STACKTRACE
> >
> > +config STACK_HASH_ORDER_SHIFT
> > + int "stack depot hash size (12 => 4KB, 20 => 1024KB)"
> > + range 12 20
> > + default 20
> > + depends on STACKDEPOT
> > + help
> > + Select the hash size as a power of 2 for the stackdepot hash
> > table.
> > + Choose a lower value to reduce the memory impact.
> > +
> > config SBITMAP
> > bool
> >
> > diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> > index 2caffc6..413c20b 100644
> > --- a/lib/stackdepot.c
> > +++ b/lib/stackdepot.c
> > @@ -142,8 +142,7 @@ static struct stack_record *depot_alloc_stack(unsigned
> > long *entries, int size,
> > return stack;
> > }
> >
> > -#define STACK_HASH_ORDER 20
> > -#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER)
> > +#define STACK_HASH_SIZE (1L << CONFIG_STACK_HASH_ORDER_SHIFT)
> > #define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
> > #define STACK_HASH_SEED 0x9747b28c
> >
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> > of Code Aurora Forum, hosted by The Linux Foundation
> > 2.7.4
> >
>
> 1. When we don't use page_owner, we don't want to waste any memory for
> stackdepot hash array.
> 2. When we use page_owner, we want to have reasonable stackdeport hash array
>
> With this configuration, it couldn't meet since we always need to
> reserve a reasonable size for the array.
> Can't we make the hash size as a kernel parameter?
> With it, we could use it like this.
>
> 1. page_owner=off, stackdepot_stack_hash=0 -> no more wasted memory
> when we don't use page_owner
> 2. page_owner=on, stackdepot_stack_hash=8M -> reasonable hash size
> when we use page_owner.
Seems we have other users like kasan, and dma_buf_ref which we introduced.
Also we can't guarantee there will not be any other users for stackdepot, so
it's better we not depend on only page owner?
>
>
> --
> Kind regards,
> Minchan Kim
>
