linux-kernel - Re: __GFP_REPEAT usage in fq_alloc

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Message-ID: <20170106161944.GW5556@dhcp22.suse.cz>
Date:   Fri, 6 Jan 2017 17:19:44 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: __GFP_REPEAT usage in fq_alloc_node

On Fri 06-01-17 17:07:43, Michal Hocko wrote:
> On Fri 06-01-17 07:39:14, Eric Dumazet wrote:
> > On Fri, Jan 6, 2017 at 7:20 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > >
> > > Hi Eric,
> > > I am currently checking kmalloc with vmalloc fallback users and convert
> > > them to a new kvmalloc helper [1]. While I am adding a support for
> > > __GFP_REPEAT to kvmalloc [2] I was wondering what is the reason to use
> > > __GFP_REPEAT in fq_alloc_node in the first place. c3bd85495aef
> > > ("pkt_sched: fq: more robust memory allocation") doesn't mention
> > > anything. Could you clarify this please?
> > >
> > > Thanks!
> > 
> > I guess this question applies to all __GFP_REPEAT usages in net/ ?
> 
> I am _currently_ interested only in those which have vmalloc fallback
> and cannot see more of them. Maybe my git grep foo needs some help.

I was obviously blind...
---
>From 8eadf8774daecdd6c4de37339216282a16920458 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Fri, 6 Jan 2017 17:03:31 +0100
Subject: [PATCH] net: use kvmalloc rather than open coded variant

fq_alloc_node, alloc_netdev_mqs and netif_alloc* open code kmalloc
with vmalloc fallback. Use the kvmalloc variant instead. Keep the
__GFP_REPEAT flag based on explanation from
Eric:
"
At the time, tests on the hardware I had in my labs showed that
vmalloc() could deliver pages spread all over the memory and that was a
small penalty (once memory is fragmented enough, not at boot time)
"

Cc: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 net/core/dev.c     | 24 +++++++++---------------
 net/sched/sch_fq.c | 12 +-----------
 2 files changed, 10 insertions(+), 26 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 56818f7eab2b..5cf2762387aa 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7111,12 +7111,10 @@ static int netif_alloc_rx_queues(struct net_device *dev)
 
 	BUG_ON(count < 1);
 
-	rx = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!rx) {
-		rx = vzalloc(sz);
-		if (!rx)
-			return -ENOMEM;
-	}
+	rx = kvzalloc(sz, GFP_KERNEL | __GFP_REPEAT);
+	if (!rx)
+		return -ENOMEM;
+
 	dev->_rx = rx;
 
 	for (i = 0; i < count; i++)
@@ -7153,12 +7151,10 @@ static int netif_alloc_netdev_queues(struct net_device *dev)
 	if (count < 1 || count > 0xffff)
 		return -EINVAL;
 
-	tx = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!tx) {
-		tx = vzalloc(sz);
-		if (!tx)
-			return -ENOMEM;
-	}
+	tx = kvzalloc(sz, GFP_KERNEL | __GFP_REPEAT);
+	if (!tx)
+		return -ENOMEM;
+
 	dev->_tx = tx;
 
 	netdev_for_each_tx_queue(dev, netdev_init_one_queue, NULL);
@@ -7691,9 +7687,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 	/* ensure 32-byte alignment of whole construct */
 	alloc_size += NETDEV_ALIGN - 1;
 
-	p = kzalloc(alloc_size, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
-	if (!p)
-		p = vzalloc(alloc_size);
+	p = kvzalloc(alloc_size, GFP_KERNEL | __GFP_REPEAT);
 	if (!p)
 		return NULL;
 
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index a4f738ac7728..594f77d89f6c 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -624,16 +624,6 @@ static void fq_rehash(struct fq_sched_data *q,
 	q->stat_gc_flows += fcnt;
 }
 
-static void *fq_alloc_node(size_t sz, int node)
-{
-	void *ptr;
-
-	ptr = kmalloc_node(sz, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN, node);
-	if (!ptr)
-		ptr = vmalloc_node(sz, node);
-	return ptr;
-}
-
 static void fq_free(void *addr)
 {
 	kvfree(addr);
@@ -650,7 +640,7 @@ static int fq_resize(struct Qdisc *sch, u32 log)
 		return 0;
 
 	/* If XPS was setup, we can allocate memory on right NUMA node */
-	array = fq_alloc_node(sizeof(struct rb_root) << log,
+	array = kvmalloc_node(sizeof(struct rb_root) << log, GFP_KERNEL | __GFP_REPEAT,
 			      netdev_queue_numa_node_read(sch->dev_queue));
 	if (!array)
 		return -ENOMEM;
-- 
2.11.0

-- 
Michal Hocko
SUSE Labs