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From: Michal Hocko <mhocko@kernel.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Anatoly Stepanov <astepanov@cloudlinux.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Theodore Ts'o" <tytso@mit.edu>
Subject: Re: [PATCH 1/6] mm: introduce kv[mz]alloc helpers
Date: Thu, 19 Jan 2017 10:56:12 +0100	[thread overview]
Message-ID: <20170119095610.GL30786@dhcp22.suse.cz> (raw)
In-Reply-To: <f1b2ce94-8448-f744-e9d0-c65f6f68fe18@nvidia.com>

On Thu 19-01-17 01:09:35, John Hubbard wrote:
[...]
> So that leaves us with maybe this for documentation?
> 
>  * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL should not be passed in.
>  * Passing in __GFP_REPEAT is supported, and will cause the following behavior:
>  * for larger (>64KB) allocations, the first part (kmalloc) will do some
>  * retrying, before falling back to vmalloc.

I am worried this is just too vague. It doesn't really help user to
decide whether "do some retrying" is what he really want's or needs.

So I would rather see the following.
"
 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. __GFP_REPEAT
 * is supported only for large (>32kB) allocations and it should be used when using
 * kmalloc is preferable because vmalloc fallback has visible performance drawbacks.
"

I would also add
"
Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
"

Does it sound any better?
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Anatoly Stepanov <astepanov@cloudlinux.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Theodore Ts'o <tytso@mit.edu>
Subject: Re: [PATCH 1/6] mm: introduce kv[mz]alloc helpers
Date: Thu, 19 Jan 2017 10:56:12 +0100	[thread overview]
Message-ID: <20170119095610.GL30786@dhcp22.suse.cz> (raw)
In-Reply-To: <f1b2ce94-8448-f744-e9d0-c65f6f68fe18@nvidia.com>

On Thu 19-01-17 01:09:35, John Hubbard wrote:
[...]
> So that leaves us with maybe this for documentation?
> 
>  * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL should not be passed in.
>  * Passing in __GFP_REPEAT is supported, and will cause the following behavior:
>  * for larger (>64KB) allocations, the first part (kmalloc) will do some
>  * retrying, before falling back to vmalloc.

I am worried this is just too vague. It doesn't really help user to
decide whether "do some retrying" is what he really want's or needs.

So I would rather see the following.
"
 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. __GFP_REPEAT
 * is supported only for large (>32kB) allocations and it should be used when using
 * kmalloc is preferable because vmalloc fallback has visible performance drawbacks.
"

I would also add
"
Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
"

Does it sound any better?
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2017-01-19  9:57 UTC|newest]

Thread overview: 129+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-12 15:37 [PATCH 0/6 v3] kvmalloc Michal Hocko
2017-01-12 15:37 ` Michal Hocko
2017-01-12 15:37 ` [PATCH 1/6] mm: introduce kv[mz]alloc helpers Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-16  4:34   ` John Hubbard
2017-01-16  4:34     ` John Hubbard
2017-01-16  8:47     ` Michal Hocko
2017-01-16  8:47       ` Michal Hocko
2017-01-16 19:09       ` John Hubbard
2017-01-16 19:09         ` John Hubbard
2017-01-16 19:40         ` Michal Hocko
2017-01-16 19:40           ` Michal Hocko
2017-01-16 21:15           ` John Hubbard
2017-01-16 21:15             ` John Hubbard
2017-01-16 21:48             ` Michal Hocko
2017-01-16 21:48               ` Michal Hocko
2017-01-16 21:57               ` John Hubbard
2017-01-16 21:57                 ` John Hubbard
2017-01-17  7:51                 ` Michal Hocko
2017-01-17  7:51                   ` Michal Hocko
2017-01-18  5:59                   ` John Hubbard
2017-01-18  5:59                     ` John Hubbard
2017-01-18  8:21                     ` Michal Hocko
2017-01-18  8:21                       ` Michal Hocko
2017-01-19  8:37                       ` John Hubbard
2017-01-19  8:37                         ` John Hubbard
2017-01-19  8:45                         ` Michal Hocko
2017-01-19  8:45                           ` Michal Hocko
2017-01-19  9:09                           ` John Hubbard
2017-01-19  9:09                             ` John Hubbard
2017-01-19  9:56                             ` Michal Hocko [this message]
2017-01-19  9:56                               ` Michal Hocko
2017-01-19 21:28                               ` John Hubbard
2017-01-19 21:28                                 ` John Hubbard
2017-01-26 12:09   ` Michal Hocko
2017-01-26 12:09     ` Michal Hocko
2017-01-30  8:42     ` Vlastimil Babka
2017-01-30  8:42       ` Vlastimil Babka
2017-01-12 15:37 ` [PATCH 2/6] mm: support __GFP_REPEAT in kvmalloc_node for >=64kB Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 16:12   ` Michael S. Tsirkin
2017-01-12 16:12     ` Michael S. Tsirkin
2017-01-14  2:42   ` Tetsuo Handa
2017-01-14  2:42     ` Tetsuo Handa
2017-01-14  8:45     ` Michal Hocko
2017-01-14  8:45       ` Michal Hocko
2017-01-24 15:40   ` Michael S. Tsirkin
2017-01-24 15:40     ` Michael S. Tsirkin
2017-01-12 15:37 ` [PATCH 3/6] rhashtable: simplify a strange allocation pattern Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 15:37 ` [PATCH 4/6] ila: " Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 15:37 ` [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded variants Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 15:57   ` David Sterba
2017-01-12 15:57     ` David Sterba
2017-01-12 15:57     ` David Sterba
2017-01-12 16:05   ` Christian Borntraeger
2017-01-12 16:05     ` Christian Borntraeger
2017-01-12 16:05     ` Christian Borntraeger
2017-01-12 16:54   ` Ilya Dryomov
2017-01-12 16:54     ` Ilya Dryomov
2017-01-12 16:54     ` Ilya Dryomov
2017-01-12 17:18     ` Michal Hocko
2017-01-12 17:18       ` Michal Hocko
2017-01-12 17:18       ` Michal Hocko
2017-01-12 17:00   ` Dan Williams
2017-01-12 17:00     ` Dan Williams
2017-01-12 17:00     ` Dan Williams
2017-01-12 17:26   ` Kees Cook
2017-01-12 17:26     ` Kees Cook
2017-01-12 17:26     ` Kees Cook
2017-01-12 17:37     ` Michal Hocko
2017-01-12 17:37       ` Michal Hocko
2017-01-12 17:37       ` Michal Hocko
2017-01-20 13:41       ` Vlastimil Babka
2017-01-20 13:41         ` Vlastimil Babka
2017-01-20 13:41         ` Vlastimil Babka
2017-01-24 15:00         ` Michal Hocko
2017-01-24 15:00           ` Michal Hocko
2017-01-24 15:00           ` Michal Hocko
2017-01-25 11:15           ` Vlastimil Babka
2017-01-25 11:15             ` Vlastimil Babka
2017-01-25 11:15             ` Vlastimil Babka
2017-01-25 13:09             ` Michal Hocko
2017-01-25 13:09               ` Michal Hocko
2017-01-25 13:09               ` Michal Hocko
2017-01-25 13:40               ` Ilya Dryomov
2017-01-25 13:40                 ` Ilya Dryomov
2017-01-25 13:40                 ` Ilya Dryomov
2017-01-12 17:29   ` Michal Hocko
2017-01-12 17:29     ` Michal Hocko
2017-01-12 17:29     ` Michal Hocko
2017-01-14  3:01     ` Tetsuo Handa
2017-01-14  3:01       ` Tetsuo Handa
2017-01-14  8:49       ` Michal Hocko
2017-01-14  8:49         ` Michal Hocko
2017-01-12 20:14   ` Boris Ostrovsky
2017-01-12 20:14     ` Boris Ostrovsky
2017-01-12 20:14     ` Boris Ostrovsky
2017-01-13  1:11   ` Dilger, Andreas
2017-01-13  1:11     ` Dilger, Andreas
2017-01-13  1:11     ` Dilger, Andreas
2017-01-14 10:56   ` Leon Romanovsky
2017-01-14 10:56     ` Leon Romanovsky
2017-01-16  7:33     ` Michal Hocko
2017-01-16  7:33       ` Michal Hocko
2017-01-16  7:33       ` Michal Hocko
2017-01-16  8:28       ` Leon Romanovsky
2017-01-16  8:28         ` Leon Romanovsky
2017-01-16  8:18   ` Tariq Toukan
2017-01-16  8:18     ` Tariq Toukan
2017-01-16  8:18     ` Tariq Toukan
2017-01-12 15:37 ` [RFC PATCH 6/6] net: use kvmalloc with __GFP_REPEAT rather than open coded variant Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-12 15:37   ` Michal Hocko
2017-01-24 15:17 ` [PATCH 0/6 v3] kvmalloc Michal Hocko
2017-01-24 15:17   ` Michal Hocko
2017-01-24 16:00   ` Eric Dumazet
2017-01-24 16:00     ` Eric Dumazet
2017-01-25 13:10     ` Michal Hocko
2017-01-25 13:10       ` Michal Hocko
2017-01-24 19:17   ` Alexei Starovoitov
2017-01-24 19:17     ` Alexei Starovoitov
2017-01-25 13:10     ` Michal Hocko
2017-01-25 13:10       ` Michal Hocko
2017-01-25 13:21       ` Michal Hocko
2017-01-25 13:21         ` Michal Hocko

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