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Message-ID: <20100902145141.GA3273@quack.suse.cz> Date: Thu, 2 Sep 2010 16:51:41 +0200 From: Jan Kara <jack@...e.cz> To: Jiri Slaby <jirislaby@...il.com> Cc: David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Neil Brown <neilb@...e.de>, Alasdair G Kergon <agk@...hat.com>, Chris Mason <chris.mason@...cle.com>, Steven Whitehouse <swhiteho@...hat.com>, Jens Axboe <jaxboe@...ionio.com>, Jan Kara <jack@...e.cz>, Frederic Weisbecker <fweisbec@...il.com>, linux-raid@...r.kernel.org, linux-btrfs@...r.kernel.org, cluster-devel@...hat.com, linux-ext4@...r.kernel.org, reiserfs-devel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [patch v2 1/5] mm: add nofail variants of kmalloc kcalloc and kzalloc On Thu 02-09-10 09:59:13, Jiri Slaby wrote: > On 09/02/2010 03:02 AM, David Rientjes wrote: > > --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -334,6 +334,57 > > @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node) > > return kmalloc_node(size, flags | __GFP_ZERO, node); } > > > > +/** + * kmalloc_nofail - infinitely loop until kmalloc() succeeds. + > > * @size: how many bytes of memory are required. + * @flags: the type > > of memory to allocate (see kmalloc). + * + * NOTE: no new callers of > > this function should be implemented! + * All memory allocations should > > be failable whenever possible. + */ +static inline void > > *kmalloc_nofail(size_t size, gfp_t flags) +{ + void *ret; + + for > > (;;) { + ret = kmalloc(size, flags); + if (ret) + > > return ret; + WARN_ON_ONCE(get_order(size) > > > PAGE_ALLOC_COSTLY_ORDER); > > This doesn't work as you expect. kmalloc will warn every time it fails. > __GFP_NOFAIL used to disable the warning. Actually what's wrong with > __GFP_NOFAIL? I cannot find a reason in the changelogs why the patches > are needed. David should probably add the reasoning to the changelogs so that he doesn't have to explain again and again ;). But if I understood it correctly, the concern is that the looping checks slightly impact fast path of the callers which do not need it. Generally, also looping for a long time inside allocator isn't a nice thing but some callers aren't able to do better for now to the patch is imperfect in this sence... Honza -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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