Messages in this thread | | | Subject | Re: Re: [PATCH v3] zram: try vmalloc() after kmalloc() | From | Kyeongdon Kim <> | Date | Tue, 24 Nov 2015 17:09:06 +0900 |
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On 2015-11-24 오전 8:28, Minchan Kim wrote: > Hello Andrew, > > On Mon, Nov 23, 2015 at 02:52:26PM -0800, Andrew Morton wrote: >> On Mon, 23 Nov 2015 15:21:15 +0900 Kyeongdon Kim > <kyeongdon.kim@lge.com> wrote: >> >> > When we're using LZ4 multi compression streams for zram swap, >> > we found out page allocation failure message in system running test. >> > That was not only once, but a few(2 - 5 times per test). >> > Also, some failure cases were continually occurring to try allocation >> > order 3. >> > >> > In order to make parallel compression private data, we should call >> > kzalloc() with order 2/3 in runtime(lzo/lz4). But if there is no order >> > 2/3 size memory to allocate in that time, page allocation fails. >> > This patch makes to use vmalloc() as fallback of kmalloc(), this >> > prevents page alloc failure warning. >> > >> > After using this, we never found warning message in running test, also >> > It could reduce process startup latency about 60-120ms in each case. >> > >> > ... >> > >> > --- a/drivers/block/zram/zcomp_lz4.c >> > +++ b/drivers/block/zram/zcomp_lz4.c >> > @@ -10,17 +10,25 @@ >> > #include <linux/kernel.h> >> > #include <linux/slab.h> >> > #include <linux/lz4.h> >> > +#include <linux/vmalloc.h> >> > +#include <linux/mm.h> >> > >> > #include "zcomp_lz4.h" >> > >> > static void *zcomp_lz4_create(void) >> > { >> > - return kzalloc(LZ4_MEM_COMPRESS, GFP_KERNEL); >> > + void *ret; >> > + >> > + ret = kzalloc(LZ4_MEM_COMPRESS, >> > + __GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC); >> > + if (!ret) >> > + ret = vzalloc(LZ4_MEM_COMPRESS); >> > + return ret; >> > } >> >> What's the reasoning behind the modification to the gfp flags? >> >> It clears __GFP_FS, __GFP_IO and even __GFP_WAIT. I suspect the latter >> two (at least) can be retained. And given that vmalloc() uses > > This function is used in swapout and fs write path so we couldn't use > those flags. > >> GFP_KERNEL, what's the point in clearing those flags for the kmalloc() >> case? > > When I reviewed this patch, I wanted to fix it with another patch > because we should handle another places in zcomp and Sergey sent it > today. But I think Sergey's patch is stable material so I hope > Kyeongdon resend this patch with fixing vmalloc part. > >> >> If this change (or something like it) remains in place, it should have >> a comment which fully explains the reasons, please. > > Kyeongdon, Could you resend this patch with fixing vzalloc part and > adding comment? > Sorry for the delay in replying, I just checked your comments and patch set.
[PATCH 1/3] zram/zcomp: use GFP_NOIO to allocate stream [PATCH 2/3] zram: try vmalloc() after kmalloc() [RFC 3/3] zram: pass gfp from zcomp frontend to backend
First of all, thanks for your summary and organized code set, and If Sergey agrees with that, I have no question about the patch 2/3.
>> > > -- > Kind regards, > Minchan Kim
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