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SubjectRe: [PATCH 6/9] net: use kvmalloc with __GFP_REPEAT rather than open coded variant
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On 01/30/2017 10:49 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> 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)
> "
>
> The way how the code is constructed means, however, that we prefer to go
> and hit the OOM killer before we fall back to the vmalloc for requests
> <=32kB (with 4kB pages) in the current code. This is rather disruptive for
> something that can be achived with the fallback. On the other hand
> __GFP_REPEAT doesn't have any useful semantic for these requests. So the
> effect of this patch is that requests smaller than 64kB will fallback to
> vmalloc esier now.

easier

Although it's somewhat of an euphemism when compared to "basically never" :)

>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> 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 be11abac89b3..707e730821a6 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -7081,12 +7081,10 @@ 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++)
> @@ -7123,12 +7121,10 @@ 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);
> @@ -7661,9 +7657,7 @@ 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;
>

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