From: Vasily Averin <vvs@virtuozzo.com>
To: Michal Hocko <mhocko@suse.com>
Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
Alexey Dobriyan <adobriyan@gmail.com>,
Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dmitry Safonov <0x7f454c46@gmail.com>
Subject: Re: [PATCH 2/2] ipc: use kmalloc for msg_queue and shmid_kernel
Date: Wed, 28 Apr 2021 08:15:10 +0300 [thread overview]
Message-ID: <70805e05-5e56-2ab9-2654-3d48e9fe5a0a@virtuozzo.com> (raw)
In-Reply-To: <YIaVKi+0VMrz5LGD@dhcp22.suse.cz>
On 4/26/21 1:25 PM, Michal Hocko wrote:
> Using kvmalloc for sub page size objects is suboptimal because kmalloc
> can easily fallback into vmalloc under memory pressure and smaller
> objects would fragment memory. Therefore replace kvmalloc by a simple
> kmalloc.
I think you're wrong here:
kvmalloc can failback to vmalloc for size > PAGE_SIZE only
Please take look at mm/util.c::kvmalloc_node()
if (size > PAGE_SIZE) {
kmalloc_flags |= __GFP_NOWARN;
if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
kmalloc_flags |= __GFP_NORETRY;
}
ret = kmalloc_node(size, kmalloc_flags, node);
/*
* It doesn't really make sense to fallback to vmalloc for sub page
* requests
*/
if (ret || size <= PAGE_SIZE)
return ret;
return __vmalloc_node(size, 1, flags, node,
__builtin_return_address(0));
For small objects kvmalloc is not much different just from kmalloc,
so the patch is mostly cosmetic.
next prev parent reply other threads:[~2021-04-28 5:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <e67f2a95-4b01-9db2-fe47-0b2210f0b138@virtuozzo.com>
2021-04-26 10:18 ` [PATCH 0/2] ipc: allocations cleanup Vasily Averin
2021-04-28 7:35 ` [PATCH v2 " Vasily Averin
2021-04-28 7:35 ` [PATCH v2 1/2] ipc sem: use kvmalloc for sem_undo allocation Vasily Averin
2021-04-28 7:35 ` [PATCH v2 2/2] ipc: use kmalloc for msg_queue and shmid_kernel Vasily Averin
2021-04-26 10:18 ` [PATCH 1/2] ipc sem: use kvmalloc for sem_undo allocation Vasily Averin
2021-04-26 10:28 ` Michal Hocko
2021-04-26 16:22 ` Shakeel Butt
2021-04-26 20:29 ` Roman Gushchin
2021-04-26 10:18 ` [PATCH 2/2] ipc: use kmalloc for msg_queue and shmid_kernel Vasily Averin
2021-04-26 10:25 ` Michal Hocko
2021-04-28 5:15 ` Vasily Averin [this message]
2021-04-28 6:33 ` Michal Hocko
2021-04-26 16:23 ` Shakeel Butt
2021-04-26 20:29 ` Roman Gushchin
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