From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
As skb page_alloc allocations tend to be big, tagging and checking all
such allocations with Hardware Tag-Based KASAN introduces a significant
slowdown in testing scenarios that extensively use the network. This is
undesirable, as Hardware Tag-Based KASAN is intended to be used in
production and thus its performance impact is crucial.
Use __GFP_KASAN_SAMPLE flag for skb page_alloc allocations to make KASAN
use sampling and tag only some of these allocations.
When running a local loopback test on a testing MTE-enabled device in sync
mode, enabling Hardware Tag-Based KASAN intoduces a 50% slowdown. Applying
this patch and setting kasan.page_alloc.sampling to a value higher than 1
allows to lower the slowdown. The performance improvement saturates around
the sampling interval value of 10, which lowers the slowdown to 20%. The
slowdown in real scenarios will likely be better.
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
net/core/skbuff.c | 4 ++--
net/core/sock.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 88fa40571d0c..fdea87deee13 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -6135,8 +6135,8 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
while (order) {
if (npages >= 1 << order) {
page = alloc_pages((gfp_mask & ~__GFP_DIRECT_RECLAIM) |
- __GFP_COMP |
- __GFP_NOWARN,
+ __GFP_COMP | __GFP_NOWARN |
+ __GFP_KASAN_SAMPLE,
order);
if (page)
goto fill_page;
diff --git a/net/core/sock.c b/net/core/sock.c
index a3ba0358c77c..f7d20070ad88 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2842,7 +2842,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
/* Avoid direct reclaim but allow kswapd to wake */
pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
__GFP_COMP | __GFP_NOWARN |
- __GFP_NORETRY,
+ __GFP_NORETRY | __GFP_KASAN_SAMPLE,
SKB_FRAG_PAGE_ORDER);
if (likely(pfrag->page)) {
pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
--
2.25.1
