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net-zerocopy: Refactor frag-is-remappable test. 

Refactor frag-is-remappable test for tcp receive zerocopy. This is
part of a patch set that introduces short-circuited hybrid copies
for small receive operations, which results in roughly 33% fewer
syscalls for small RPC scenarios.

Signed-off-by: Arjun Roy <arjunroy@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Arjun Roy 2020-12-02 14:53:45 -08:00 committed by Jakub Kicinski
parent 7fba5309ef
commit 98917cf0d6
1 changed files with 26 additions and 8 deletions
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34
net/ipv4/tcp.c
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@ -1780,6 +1780,26 @@ static skb_frag_t *skb_advance_to_frag(struct sk_buff *skb, u32 offset_skb,
return frag;
}
static bool can_map_frag(const skb_frag_t *frag)
{
return skb_frag_size(frag) == PAGE_SIZE && !skb_frag_off(frag);
}
static int find_next_mappable_frag(const skb_frag_t *frag,
int remaining_in_skb)
{
int offset = 0;
if (likely(can_map_frag(frag)))
return 0;
while (offset < remaining_in_skb && !can_map_frag(frag)) {
offset += skb_frag_size(frag);
++frag;
}
return offset;
}
static int tcp_copy_straggler_data(struct tcp_zerocopy_receive *zc,
struct sk_buff *skb, u32 copylen,
u32 *offset, u32 *seq)
@ -1905,6 +1925,8 @@ static int tcp_zerocopy_receive(struct sock *sk,
ret = 0;
curr_addr = address;
while (length + PAGE_SIZE <= zc->length) {
int mappable_offset;
if (zc->recv_skip_hint < PAGE_SIZE) {
u32 offset_frag;
@ -1932,15 +1954,11 @@ static int tcp_zerocopy_receive(struct sock *sk,
if (!frags || offset_frag)
break;
}
if (skb_frag_size(frags) != PAGE_SIZE || skb_frag_off(frags)) {
int remaining = zc->recv_skip_hint;
while (remaining && (skb_frag_size(frags) != PAGE_SIZE ||
skb_frag_off(frags))) {
remaining -= skb_frag_size(frags);
frags++;
}
zc->recv_skip_hint -= remaining;
mappable_offset = find_next_mappable_frag(frags,
zc->recv_skip_hint);
if (mappable_offset) {
zc->recv_skip_hint = mappable_offset;
break;
}
pages[pg_idx] = skb_frag_page(frags);