lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 24 Nov 2015 09:30:27 +0900 From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org, sergey.senozhatsky.work@...il.com Subject: Re: [PATCH] zram/zcomp: use GFP_NOIO to allocate streams On (11/23/15 15:18), Andrew Morton wrote: [..] > > --- a/drivers/block/zram/zcomp_lz4.c > > +++ b/drivers/block/zram/zcomp_lz4.c > > @@ -20,10 +20,13 @@ static void *zcomp_lz4_create(void) > > void *ret; > > > > ret = kzalloc(LZ4_MEM_COMPRESS, > > - __GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC); > > - if (!ret) > > - ret = vzalloc(LZ4_MEM_COMPRESS); > > - return ret; > > + __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC); > > But here we've still lost __GFP_RECLAIM, unnecessarily. And it's quite > unclear why __GFP_NORETRY and __GFP_NOMEMALLOC are being used. __GFP_NORETRY we are guaranteed to have at least one compression stream, so sooner or later every IO operation will be served. any IO that has failed in zcomp_lz4_create() or zcomp_lzo_create() will simply wait for already available compression stream to become idle. so this allocation is not so dramatically important - we just increase the level of parallelism (N idle streams let N IO operations to execute concurrently). apart from that we are in a low memory condition (or whatever was the reason the kernel failed to allocate LZ4_MEM_COMPRESS or LZO1X_MEM_COMPRESS) and we can avoid pressuring the kernel furher. for the same reason __GFP_NOMEMALLOC is used -- we don't want to waste an emergency memory for compression streams. I agree on __GFP_RECLAIM. Thanks. > IOW, why not simply use (GFP_NOIO|__GFP_NOWARN)? GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC ? -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists