linux-kernel - Re: [PATCH V4] mlx4_core: allocate ICM memory in page size chunks

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Message-ID: <20180604131104.GS19202@dhcp22.suse.cz>
Date:   Mon, 4 Jun 2018 15:11:04 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>, qing.huang@...cle.com,
        tariqt@...lanox.com, haakon.bugge@...cle.com,
        yanjun.zhu@...cle.com, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        gi-oh.kim@...fitbricks.com
Subject: Re: [PATCH V4] mlx4_core: allocate ICM memory in page size chunks

On Thu 31-05-18 11:10:22, Michal Hocko wrote:
> On Thu 31-05-18 10:55:32, Michal Hocko wrote:
> > On Thu 31-05-18 04:35:31, Eric Dumazet wrote:
> [...]
> > > I merely copied/pasted from alloc_skb_with_frags() :/
> > 
> > I will have a look at it. Thanks!
> 
> OK, so this is an example of an incremental development ;).
> 
> __GFP_NORETRY was added by ed98df3361f0 ("net: use __GFP_NORETRY for
> high order allocations") to prevent from OOM killer. Yet this was
> not enough because fb05e7a89f50 ("net: don't wait for order-3 page
> allocation") didn't want an excessive reclaim for non-costly orders
> so it made it completely NOWAIT while it preserved __GFP_NORETRY in
> place which is now redundant. Should I send a patch?

Just in case you are interested
---
>From 5010543ed6f73e4c00367801486dca8d5c63b2ce Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Mon, 4 Jun 2018 15:07:37 +0200
Subject: [PATCH] net: cleanup gfp mask in alloc_skb_with_frags

alloc_skb_with_frags uses __GFP_NORETRY for non-sleeping allocations
which is just a noop and a little bit confusing.

__GFP_NORETRY was added by ed98df3361f0 ("net: use __GFP_NORETRY for
high order allocations") to prevent from the OOM killer. Yet this was
not enough because fb05e7a89f50 ("net: don't wait for order-3 page
allocation") didn't want an excessive reclaim for non-costly orders
so it made it completely NOWAIT while it preserved __GFP_NORETRY in
place which is now redundant.

Drop the pointless __GFP_NORETRY because this function is used as
copy&paste source for other places.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 net/core/skbuff.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 857e4e6f751a..c1f22adc30de 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5239,8 +5239,7 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
 			if (npages >= 1 << order) {
 				page = alloc_pages((gfp_mask & ~__GFP_DIRECT_RECLAIM) |
 						   __GFP_COMP |
-						   __GFP_NOWARN |
-						   __GFP_NORETRY,
+						   __GFP_NOWARN,
 						   order);
 				if (page)
 					goto fill_page;
-- 
2.17.0

-- 
Michal Hocko
SUSE Labs