From: David Howells <dhowells@redhat.com>
To: Pavel Begunkov <asml.silence@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
Alexander Viro <viro@zeniv.linux.org.uk>
Cc: dhowells@redhat.com,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 00/29] RFC: iov_iter: Switch to using an ops table
Date: Sat, 21 Nov 2020 14:13:21 +0000 [thread overview]
Message-ID: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> (raw)
Hi Pavel, Willy, Jens, Al,
I had a go switching the iov_iter stuff away from using a type bitmask to
using an ops table to get rid of the if-if-if-if chains that are all over
the place. After I pushed it, someone pointed me at Pavel's two patches.
I have another iterator class that I want to add - which would lengthen the
if-if-if-if chains. A lot of the time, there's a conditional clause at the
beginning of a function that just jumps off to a type-specific handler or
to reject the operation for that type. An ops table can just point to that
instead.
As far as I can tell, there's no difference in performance in most cases,
though doing AFS-based kernel compiles appears to take less time (down from
3m20 to 2m50), which might make sense as that uses iterators a lot - but
there are too many variables in that for that to be a good benchmark (I'm
dealing with a remote server, for a start).
Can someone recommend a good way to benchmark this properly? The problem
is that the difference this makes relative to the amount of time taken to
actually do I/O is tiny.
I've tried TCP transfers using the following sink program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <netinet/in.h>
#define OSERROR(X, Y) do { if ((long)(X) == -1) { perror(Y); exit(1); } } while(0)
static unsigned char buffer[512 * 1024] __attribute__((aligned(4096)));
int main(int argc, char *argv[])
{
struct sockaddr_in sin = { .sin_family = AF_INET, .sin_port = htons(5555) };
int sfd, afd;
sfd = socket(AF_INET, SOCK_STREAM, 0);
OSERROR(sfd, "socket");
OSERROR(bind(sfd, (struct sockaddr *)&sin, sizeof(sin)), "bind");
OSERROR(listen(sfd, 1), "listen");
for (;;) {
afd = accept(sfd, NULL, NULL);
if (afd != -1) {
while (read(afd, buffer, sizeof(buffer)) > 0) {}
close(afd);
}
}
}
and send program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#define OSERROR(X, Y) do { if ((long)(X) == -1) { perror(Y); exit(1); } } while(0)
static unsigned char buffer[512*1024] __attribute__((aligned(4096)));
int main(int argc, char *argv[])
{
struct sockaddr_in sin = { .sin_family = AF_INET, .sin_port = htons(5555) };
struct hostent *h;
ssize_t size, r, o;
int cfd;
if (argc != 3) {
fprintf(stderr, "tcp-gen <server> <size>\n");
exit(2);
}
size = strtoul(argv[2], NULL, 0);
if (size <= 0) {
fprintf(stderr, "Bad size\n");
exit(2);
}
h = gethostbyname(argv[1]);
if (!h) {
fprintf(stderr, "%s: %s\n", argv[1], hstrerror(h_errno));
exit(3);
}
if (!h->h_addr_list[0]) {
fprintf(stderr, "%s: No addresses\n", argv[1]);
exit(3);
}
memcpy(&sin.sin_addr, h->h_addr_list[0], h->h_length);
cfd = socket(AF_INET, SOCK_STREAM, 0);
OSERROR(cfd, "socket");
OSERROR(connect(cfd, (struct sockaddr *)&sin, sizeof(sin)), "connect");
do {
r = size > sizeof(buffer) ? sizeof(buffer) : size;
size -= r;
o = 0;
do {
ssize_t w = write(cfd, buffer + o, r - o);
OSERROR(w, "write");
o += w;
} while (o < r);
} while (size > 0);
OSERROR(close(cfd), "close/c");
return 0;
}
since the socket interface uses iterators. It seems to show no difference.
One side note, though: I've been doing 10GiB same-machine transfers, and it
takes either ~2.5s or ~0.87s and rarely in between, with or without these
patches, alternating apparently randomly between the two times.
The patches can be found here:
https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-ops
David
---
David Howells (29):
iov_iter: Switch to using a table of operations
iov_iter: Split copy_page_to_iter()
iov_iter: Split iov_iter_fault_in_readable
iov_iter: Split the iterate_and_advance() macro
iov_iter: Split copy_to_iter()
iov_iter: Split copy_mc_to_iter()
iov_iter: Split copy_from_iter()
iov_iter: Split the iterate_all_kinds() macro
iov_iter: Split copy_from_iter_full()
iov_iter: Split copy_from_iter_nocache()
iov_iter: Split copy_from_iter_flushcache()
iov_iter: Split copy_from_iter_full_nocache()
iov_iter: Split copy_page_from_iter()
iov_iter: Split iov_iter_zero()
iov_iter: Split copy_from_user_atomic()
iov_iter: Split iov_iter_advance()
iov_iter: Split iov_iter_revert()
iov_iter: Split iov_iter_single_seg_count()
iov_iter: Split iov_iter_alignment()
iov_iter: Split iov_iter_gap_alignment()
iov_iter: Split iov_iter_get_pages()
iov_iter: Split iov_iter_get_pages_alloc()
iov_iter: Split csum_and_copy_from_iter()
iov_iter: Split csum_and_copy_from_iter_full()
iov_iter: Split csum_and_copy_to_iter()
iov_iter: Split iov_iter_npages()
iov_iter: Split dup_iter()
iov_iter: Split iov_iter_for_each_range()
iov_iter: Remove iterate_all_kinds() and iterate_and_advance()
lib/iov_iter.c | 1440 +++++++++++++++++++++++++++++++-----------------
1 file changed, 934 insertions(+), 506 deletions(-)
next reply other threads:[~2020-11-21 14:13 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-21 14:13 David Howells [this message]
2020-11-21 14:13 ` [PATCH 01/29] iov_iter: Switch to using a table of operations David Howells
2020-11-21 14:31 ` Pavel Begunkov
2020-11-23 23:21 ` Pavel Begunkov
2020-11-21 18:21 ` Linus Torvalds
2020-12-11 1:30 ` Al Viro
2020-11-22 13:33 ` David Howells
2020-11-22 13:58 ` David Laight
2020-11-22 19:22 ` Linus Torvalds
2020-11-22 22:34 ` David Laight
2020-11-22 22:46 ` David Laight
2020-11-23 8:05 ` Christoph Hellwig
2020-11-23 10:31 ` David Howells
2020-11-23 23:42 ` Pavel Begunkov
2020-11-24 12:50 ` David Howells
2020-11-24 15:30 ` Jens Axboe
2020-11-27 17:14 ` David Howells
2020-11-23 11:14 ` David Howells
[not found] ` <20201203064536.GE27350@xsang-OptiPlex-9020>
2020-12-03 17:47 ` [iov_iter] 9bd0e337c6: will-it-scale.per_process_ops -4.8% regression Linus Torvalds
2020-12-03 17:50 ` Jens Axboe
2020-12-04 11:50 ` David Howells
2020-12-04 11:51 ` David Howells
2020-12-07 13:10 ` Oliver Sang
2020-12-07 13:20 ` David Howells
2020-11-21 14:13 ` [PATCH 02/29] iov_iter: Split copy_page_to_iter() David Howells
2020-11-21 14:13 ` [PATCH 03/29] iov_iter: Split iov_iter_fault_in_readable David Howells
2020-11-21 14:13 ` [PATCH 04/29] iov_iter: Split the iterate_and_advance() macro David Howells
2020-11-21 14:14 ` [PATCH 05/29] iov_iter: Split copy_to_iter() David Howells
2020-11-21 14:14 ` [PATCH 06/29] iov_iter: Split copy_mc_to_iter() David Howells
2020-11-21 14:14 ` [PATCH 07/29] iov_iter: Split copy_from_iter() David Howells
2020-11-21 14:14 ` [PATCH 08/29] iov_iter: Split the iterate_all_kinds() macro David Howells
2020-11-21 14:14 ` [PATCH 09/29] iov_iter: Split copy_from_iter_full() David Howells
2020-11-21 14:14 ` [PATCH 10/29] iov_iter: Split copy_from_iter_nocache() David Howells
2020-11-21 14:14 ` [PATCH 11/29] iov_iter: Split copy_from_iter_flushcache() David Howells
2020-11-21 14:14 ` [PATCH 12/29] iov_iter: Split copy_from_iter_full_nocache() David Howells
2020-11-21 14:15 ` [PATCH 13/29] iov_iter: Split copy_page_from_iter() David Howells
2020-11-21 14:15 ` [PATCH 14/29] iov_iter: Split iov_iter_zero() David Howells
2020-11-21 14:15 ` [PATCH 15/29] iov_iter: Split copy_from_user_atomic() David Howells
2020-11-21 14:15 ` [PATCH 16/29] iov_iter: Split iov_iter_advance() David Howells
2020-11-21 14:15 ` [PATCH 17/29] iov_iter: Split iov_iter_revert() David Howells
2020-11-21 14:15 ` [PATCH 18/29] iov_iter: Split iov_iter_single_seg_count() David Howells
2020-11-21 14:15 ` [PATCH 19/29] iov_iter: Split iov_iter_alignment() David Howells
2020-11-21 14:15 ` [PATCH 20/29] iov_iter: Split iov_iter_gap_alignment() David Howells
2020-11-21 14:16 ` [PATCH 21/29] iov_iter: Split iov_iter_get_pages() David Howells
2020-11-21 14:16 ` [PATCH 22/29] iov_iter: Split iov_iter_get_pages_alloc() David Howells
2020-11-21 14:16 ` [PATCH 23/29] iov_iter: Split csum_and_copy_from_iter() David Howells
2020-11-21 14:16 ` [PATCH 24/29] iov_iter: Split csum_and_copy_from_iter_full() David Howells
2020-11-21 14:16 ` [PATCH 25/29] iov_iter: Split csum_and_copy_to_iter() David Howells
2020-11-21 14:16 ` [PATCH 26/29] iov_iter: Split iov_iter_npages() David Howells
2020-11-21 14:16 ` [PATCH 27/29] iov_iter: Split dup_iter() David Howells
2020-11-21 14:17 ` [PATCH 28/29] iov_iter: Split iov_iter_for_each_range() David Howells
2020-11-21 14:17 ` [PATCH 29/29] iov_iter: Remove iterate_all_kinds() and iterate_and_advance() David Howells
2020-11-21 14:34 ` [PATCH 00/29] RFC: iov_iter: Switch to using an ops table Pavel Begunkov
2020-11-21 18:23 ` Linus Torvalds
2020-12-11 3:24 ` Matthew Wilcox
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