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Date: Wed, 20 Aug 2014 08:46:21 +0900
From: Minchan Kim <minchan@...nel.org>
To: Seth Jennings <sjennings@...iantweb.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Jerome Marchand <jmarchan@...hat.com>, juno.choi@....com,
seungho1.park@....com, Luigi Semenzato <semenzato@...gle.com>,
Nitin Gupta <ngupta@...are.org>,
Dan Streetman <ddstreet@...e.org>, ds2horner@...il.com
Subject: Re: [PATCH v2 2/4] zsmalloc: change return value unit of
zs_get_total_size_bytes
Hey Seth,
On Tue, Aug 19, 2014 at 09:46:28AM -0500, Seth Jennings wrote:
> On Tue, Aug 19, 2014 at 04:54:45PM +0900, Minchan Kim wrote:
> > zs_get_total_size_bytes returns a amount of memory zsmalloc
> > consumed with *byte unit* but zsmalloc operates *page unit*
> > rather than byte unit so let's change the API so benefit
> > we could get is that reduce unnecessary overhead
> > (ie, change page unit with byte unit) in zsmalloc.
> >
> > Now, zswap can rollback to zswap_pool_pages.
> > Over to zswap guys ;-)
>
> I don't think that's how is it done :-/ Changing the API for a
> component that has two users, changing one, then saying "hope you guys
> change your newly broken stuff".
I don't get it. The zsmalloc's zs_zpool_total_size returns u64 with bytes,
not pages so what's broken stuff you mentioned?
static u64 zs_zpool_total_size(void *pool)
{
- return zs_get_total_size_bytes(pool);
+ return zs_get_total_size(pool) << PAGE_SHIFT;
}
Thing I nudged to you is just you could roll back to pages count
instead of bytes if zswap guys want it and I dont' want it myself
for avoding unnecessary noise for this patchset's purpose.
>
> I know you would rather not move zram to the zpool API but doing so
> would avoid situations like this.
>
> Anyway, this does break the zpool API and by extension zswap, and that
> needs to be addressed in this patch or we create a point in the commit
> history where it is broken.
>
> Quick glance:
> - zpool_get_total_size() return type is u64 but this patch changes to
> unsigned long. Now mismatches between zbud and zsmalloc.
Nope. zs_zpool_total_size returns u64 with PAGE_SHIFT.
> - zbud_zpool_total_size needs to return pages, not bytes
It's up to you, not me.
> - as you noted s/pool_total_size/pool_pages/g in zswap.c plus
> modification to zswap_is_full()
I didn't mean it. Sorry for the confusing.
If I miss your point, let me know it.
Thanks.
>
> Thanks,
> Seth
>
> >
> > Signed-off-by: Minchan Kim <minchan@...nel.org>
> > ---
> > drivers/block/zram/zram_drv.c | 4 ++--
> > include/linux/zsmalloc.h | 2 +-
> > mm/zsmalloc.c | 10 +++++-----
> > 3 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index d00831c3d731..302dd37bcea3 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -103,10 +103,10 @@ static ssize_t mem_used_total_show(struct device *dev,
> >
> > down_read(&zram->init_lock);
> > if (init_done(zram))
> > - val = zs_get_total_size_bytes(meta->mem_pool);
> > + val = zs_get_total_size(meta->mem_pool);
> > up_read(&zram->init_lock);
> >
> > - return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
> > + return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
> > }
> >
> > static ssize_t max_comp_streams_show(struct device *dev,
> > diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
> > index e44d634e7fb7..105b56e45d23 100644
> > --- a/include/linux/zsmalloc.h
> > +++ b/include/linux/zsmalloc.h
> > @@ -46,6 +46,6 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
> > enum zs_mapmode mm);
> > void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
> >
> > -u64 zs_get_total_size_bytes(struct zs_pool *pool);
> > +unsigned long zs_get_total_size(struct zs_pool *pool);
> >
> > #endif
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index a65924255763..80408a1da03a 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -299,7 +299,7 @@ static void zs_zpool_unmap(void *pool, unsigned long handle)
> >
> > static u64 zs_zpool_total_size(void *pool)
> > {
> > - return zs_get_total_size_bytes(pool);
> > + return zs_get_total_size(pool) << PAGE_SHIFT;
> > }
> >
> > static struct zpool_driver zs_zpool_driver = {
> > @@ -1186,16 +1186,16 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
> > }
> > EXPORT_SYMBOL_GPL(zs_unmap_object);
> >
> > -u64 zs_get_total_size_bytes(struct zs_pool *pool)
> > +unsigned long zs_get_total_size(struct zs_pool *pool)
> > {
> > - u64 npages;
> > + unsigned long npages;
> >
> > spin_lock(&pool->stat_lock);
> > npages = pool->pages_allocated;
> > spin_unlock(&pool->stat_lock);
> > - return npages << PAGE_SHIFT;
> > + return npages;
> > }
> > -EXPORT_SYMBOL_GPL(zs_get_total_size_bytes);
> > +EXPORT_SYMBOL_GPL(zs_get_total_size);
> >
> > module_init(zs_init);
> > module_exit(zs_exit);
> > --
> > 2.0.0
> >
> --
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--
Kind regards,
Minchan Kim
--
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