From: Michal Hocko <mhocko@kernel.org>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Huang Ying <ying.huang@intel.com>,
linux-kernel@vger.kernel.org, Aaron Lu <aaron.lu@intel.com>
Subject: Re: [PATCH v2] mm: use kvzalloc for swap_info_struct allocation
Date: Mon, 5 Nov 2018 15:11:56 +0100 [thread overview]
Message-ID: <20181105141156.GB10132@dhcp22.suse.cz> (raw)
In-Reply-To: <fc23172d-3c75-21e2-d551-8b1808cbe593@virtuozzo.com>
On Mon 05-11-18 14:17:01, Vasily Averin wrote:
> commit a2468cc9bfdf ("swap: choose swap device according to numa node")
> changed 'avail_lists' field of 'struct swap_info_struct' to an array.
> In popular linux distros it increased size of swap_info_struct up to
> 40 Kbytes and now swap_info_struct allocation requires order-4 page.
> Switch to kvzmalloc allows to avoid unexpected allocation failures.
While this fixes the most visible issue is this a good long term
solution? Aren't we wasting memory without a good reason? IIRC our limit
for swap files/devices is much smaller than potential NUMA nodes numbers
so we can safely expect that would be only few numa affine nodes. I am
not really familiar with the rework which has added numa node awareness
but I wouls assueme that we should either go with one global table with
a linked list of possible swap_info structure per numa node or use a
sparse array.
That being said I am not really objecting to this patch as it is simple
and backportable to older (stable kernels).
I would even dare to add
Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node")
because not being able to add a swap space on a fragmented system looks
like a regression to me.
> Acked-by: Aaron Lu <aaron.lu@intel.com>
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/swapfile.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 644f746e167a..8688ae65ef58 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> unsigned int type;
> int i;
>
> - p = kzalloc(sizeof(*p), GFP_KERNEL);
> + p = kvzalloc(sizeof(*p), GFP_KERNEL);
> if (!p)
> return ERR_PTR(-ENOMEM);
>
> @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> }
> if (type >= MAX_SWAPFILES) {
> spin_unlock(&swap_lock);
> - kfree(p);
> + kvfree(p);
> return ERR_PTR(-EPERM);
> }
> if (type >= nr_swapfiles) {
> @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void)
> smp_wmb();
> nr_swapfiles++;
> } else {
> - kfree(p);
> + kvfree(p);
> p = swap_info[type];
> /*
> * Do not memset this entry: a racing procfs swap_next()
> --
> 2.17.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-11-05 14:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-04 22:13 [PATCH 1/2] mm: use kvzalloc for swap_info_struct allocation Vasily Averin
2018-11-05 0:50 ` Huang, Ying
2018-11-05 4:59 ` Vasily Averin
2018-11-05 5:16 ` Huang, Ying
2018-11-05 6:10 ` Aaron Lu
2018-11-05 11:17 ` [PATCH v2] " Vasily Averin
2018-11-05 14:11 ` Michal Hocko [this message]
2018-11-05 14:27 ` Aaron Lu
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