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| author | Paolo Abeni <pabeni@redhat.com> | 2022-09-28 10:43:09 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2022-09-29 18:48:15 -0700 |
| commit | dbae2b062824fc2d35ae2d5df2f500626c758e80 (patch) | |
| tree | d946ed8bfe8065c876dd40d230d7ab11155bd90d /net/core/dev.c | |
| parent | 7cba18332e3635aaae60e4e7d4e52849de50d91b (diff) | |
| download | linux-dbae2b062824fc2d35ae2d5df2f500626c758e80.tar.gz | |
net: skb: introduce and use a single page frag cache
After commit 3226b158e67c ("net: avoid 32 x truesize under-estimation
for tiny skbs") we are observing 10-20% regressions in performance
tests with small packets. The perf trace points to high pressure on
the slab allocator.
This change tries to improve the allocation schema for small packets
using an idea originally suggested by Eric: a new per CPU page frag is
introduced and used in __napi_alloc_skb to cope with small allocation
requests.
To ensure that the above does not lead to excessive truesize
underestimation, the frag size for small allocation is inflated to 1K
and all the above is restricted to build with 4K page size.
Note that we need to update accordingly the run-time check introduced
with commit fd9ea57f4e95 ("net: add napi_get_frags_check() helper").
Alex suggested a smart page refcount schema to reduce the number
of atomic operations and deal properly with pfmemalloc pages.
Under small packet UDP flood, I measure a 15% peak tput increases.
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Suggested-by: Alexander H Duyck <alexanderduyck@fb.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://lore.kernel.org/r/6b6f65957c59f86a353fc09a5127e83a32ab5999.1664350652.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core/dev.c')
| -rw-r--r-- | net/core/dev.c | 17 |
1 files changed, 0 insertions, 17 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index d66c73c1c7345..fa53830d06839 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6358,23 +6358,6 @@ int dev_set_threaded(struct net_device *dev, bool threaded) } EXPORT_SYMBOL(dev_set_threaded); -/* Double check that napi_get_frags() allocates skbs with - * skb->head being backed by slab, not a page fragment. - * This is to make sure bug fixed in 3226b158e67c - * ("net: avoid 32 x truesize under-estimation for tiny skbs") - * does not accidentally come back. - */ -static void napi_get_frags_check(struct napi_struct *napi) -{ - struct sk_buff *skb; - - local_bh_disable(); - skb = napi_get_frags(napi); - WARN_ON_ONCE(skb && skb->head_frag); - napi_free_frags(napi); - local_bh_enable(); -} - void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi, int (*poll)(struct napi_struct *, int), int weight) { |