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authorArjun Roy <arjunroy@google.com>2020-06-08 03:54:41 +0200
committerDavid S. Miller <davem@davemloft.net>2020-06-09 04:08:17 +0200
commit3763a24c727ecf236358a81ee749e5fcab1c972a (patch)
tree9f841e8d82490893edf6d827a4a9bbc53f647d76
parentnet/tls(TLS_SW): Add selftest for 'chunked' sendfile test (diff)
downloadlinux-3763a24c727ecf236358a81ee749e5fcab1c972a.tar.xz
linux-3763a24c727ecf236358a81ee749e5fcab1c972a.zip
net-zerocopy: use vm_insert_pages() for tcp rcv zerocopy
Use vm_insert_pages() for tcp receive zerocopy. Spin lock cycles (as reported by perf) drop from a couple of percentage points to a fraction of a percent. This results in a roughly 6% increase in efficiency, measured roughly as zerocopy receive count divided by CPU utilization. The intention of this patchset is to reduce atomic ops for tcp zerocopy receives, which normally hits the same spinlock multiple times consecutively. [akpm@linux-foundation.org: suppress gcc-7.2.0 warning] Link: http://lkml.kernel.org/r/20200128025958.43490-3-arjunroy.kdev@gmail.com 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> Cc: David Miller <davem@davemloft.net> Cc: Matthew Wilcox <willy@infradead.org> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp.c70
1 files changed, 63 insertions, 7 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 15d47d5e7951..ecbba0abd3e5 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1742,14 +1742,48 @@ int tcp_mmap(struct file *file, struct socket *sock,
}
EXPORT_SYMBOL(tcp_mmap);
+static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma,
+ struct page **pages,
+ unsigned long pages_to_map,
+ unsigned long *insert_addr,
+ u32 *length_with_pending,
+ u32 *seq,
+ struct tcp_zerocopy_receive *zc)
+{
+ unsigned long pages_remaining = pages_to_map;
+ int bytes_mapped;
+ int ret;
+
+ ret = vm_insert_pages(vma, *insert_addr, pages, &pages_remaining);
+ bytes_mapped = PAGE_SIZE * (pages_to_map - pages_remaining);
+ /* Even if vm_insert_pages fails, it may have partially succeeded in
+ * mapping (some but not all of the pages).
+ */
+ *seq += bytes_mapped;
+ *insert_addr += bytes_mapped;
+ if (ret) {
+ /* But if vm_insert_pages did fail, we have to unroll some state
+ * we speculatively touched before.
+ */
+ const int bytes_not_mapped = PAGE_SIZE * pages_remaining;
+ *length_with_pending -= bytes_not_mapped;
+ zc->recv_skip_hint += bytes_not_mapped;
+ }
+ return ret;
+}
+
static int tcp_zerocopy_receive(struct sock *sk,
struct tcp_zerocopy_receive *zc)
{
unsigned long address = (unsigned long)zc->address;
u32 length = 0, seq, offset, zap_len;
+ #define PAGE_BATCH_SIZE 8
+ struct page *pages[PAGE_BATCH_SIZE];
const skb_frag_t *frags = NULL;
struct vm_area_struct *vma;
struct sk_buff *skb = NULL;
+ unsigned long pg_idx = 0;
+ unsigned long curr_addr;
struct tcp_sock *tp;
int inq;
int ret;
@@ -1762,6 +1796,8 @@ static int tcp_zerocopy_receive(struct sock *sk,
sock_rps_record_flow(sk);
+ tp = tcp_sk(sk);
+
down_read(&current->mm->mmap_sem);
vma = find_vma(current->mm, address);
@@ -1771,7 +1807,6 @@ static int tcp_zerocopy_receive(struct sock *sk,
}
zc->length = min_t(unsigned long, zc->length, vma->vm_end - address);
- tp = tcp_sk(sk);
seq = tp->copied_seq;
inq = tcp_inq(sk);
zc->length = min_t(u32, zc->length, inq);
@@ -1783,8 +1818,20 @@ static int tcp_zerocopy_receive(struct sock *sk,
zc->recv_skip_hint = zc->length;
}
ret = 0;
+ curr_addr = address;
while (length + PAGE_SIZE <= zc->length) {
if (zc->recv_skip_hint < PAGE_SIZE) {
+ /* If we're here, finish the current batch. */
+ if (pg_idx) {
+ ret = tcp_zerocopy_vm_insert_batch(vma, pages,
+ pg_idx,
+ &curr_addr,
+ &length,
+ &seq, zc);
+ if (ret)
+ goto out;
+ pg_idx = 0;
+ }
if (skb) {
if (zc->recv_skip_hint > 0)
break;
@@ -1793,7 +1840,6 @@ static int tcp_zerocopy_receive(struct sock *sk,
} else {
skb = tcp_recv_skb(sk, seq, &offset);
}
-
zc->recv_skip_hint = skb->len - offset;
offset -= skb_headlen(skb);
if ((int)offset < 0 || skb_has_frag_list(skb))
@@ -1817,14 +1863,24 @@ static int tcp_zerocopy_receive(struct sock *sk,
zc->recv_skip_hint -= remaining;
break;
}
- ret = vm_insert_page(vma, address + length,
- skb_frag_page(frags));
- if (ret)
- break;
+ pages[pg_idx] = skb_frag_page(frags);
+ pg_idx++;
length += PAGE_SIZE;
- seq += PAGE_SIZE;
zc->recv_skip_hint -= PAGE_SIZE;
frags++;
+ if (pg_idx == PAGE_BATCH_SIZE) {
+ ret = tcp_zerocopy_vm_insert_batch(vma, pages, pg_idx,
+ &curr_addr, &length,
+ &seq, zc);
+ if (ret)
+ goto out;
+ pg_idx = 0;
+ }
+ }
+ if (pg_idx) {
+ ret = tcp_zerocopy_vm_insert_batch(vma, pages, pg_idx,
+ &curr_addr, &length, &seq,
+ zc);
}
out:
up_read(&current->mm->mmap_sem);