Unverified Commit f017b0a4 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Christian Brauner
Browse files

pipe: don't update {a,c,m}time for anonymous pipes 



These numbers are visible in fstat() but hopefully nobody uses this
information and file_accessed/file_update_time are not that cheap.
Stupid test-case:

	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <assert.h>
	#include <sys/ioctl.h>
	#include <sys/time.h>

	static char buf[17 * 4096];
	static struct timeval TW, TR;

	int wr(int fd, int size)
	{
		int c, r;
		struct timeval t0, t1;

		gettimeofday(&t0, NULL);
		for (c = 0; (r = write(fd, buf, size)) > 0; c += r);
		gettimeofday(&t1, NULL);
		timeradd(&TW, &t1, &TW);
		timersub(&TW, &t0, &TW);

		return c;
	}

	int rd(int fd, int size)
	{
		int c, r;
		struct timeval t0, t1;

		gettimeofday(&t0, NULL);
		for (c = 0; (r = read(fd, buf, size)) > 0; c += r);
		gettimeofday(&t1, NULL);
		timeradd(&TR, &t1, &TR);
		timersub(&TR, &t0, &TR);

		return c;
	}

	int main(int argc, const char *argv[])
	{
		int fd[2], nb = 1, loop, size;

		assert(argc == 3);
		loop = atoi(argv[1]);
		size = atoi(argv[2]);

		assert(pipe(fd) == 0);
		assert(ioctl(fd[0], FIONBIO, &nb) == 0);
		assert(ioctl(fd[1], FIONBIO, &nb) == 0);

		assert(size <= sizeof(buf));
		while (loop--)
			assert(wr(fd[1], size) == rd(fd[0], size));

		struct timeval tt;
		timeradd(&TW, &TR, &tt);
		printf("TW = %lu.%03lu TR = %lu.%03lu TT = %lu.%03lu\n",
			TW.tv_sec, TW.tv_usec/1000,
			TR.tv_sec, TR.tv_usec/1000,
			tt.tv_sec, tt.tv_usec/1000);

		return 0;
	}

Before:
	# for i in 1 2 3; do /host/tmp/test 10000 100; done
	TW = 8.047 TR = 5.845 TT = 13.893
	TW = 8.091 TR = 5.872 TT = 13.963
	TW = 8.083 TR = 5.885 TT = 13.969
After:
	# for i in 1 2 3; do /host/tmp/test 10000 100; done
	TW = 4.752 TR = 4.664 TT = 9.416
	TW = 4.684 TR = 4.608 TT = 9.293
	TW = 4.736 TR = 4.652 TT = 9.388

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250205181812.GC13817@redhat.com


Tested-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 262b2fa9

fs/pipe.c

+29 −12
Original line number Diff line number Diff line
@@ -248,7 +248,7 @@ static inline unsigned int pipe_update_tail(struct pipe_inode_info *pipe, 
}



static ssize_t

pipe_read(struct kiocb *iocb, struct iov_iter *to)

anon_pipe_read(struct kiocb *iocb, struct iov_iter *to)

{

	size_t total_len = iov_iter_count(to);

	struct file *filp = iocb->ki_filp;
@@ -404,8 +404,15 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) 
	if (wake_next_reader)

		wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);

	kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);

	return ret;

}



static ssize_t

fifo_pipe_read(struct kiocb *iocb, struct iov_iter *to)

{

	int ret = anon_pipe_read(iocb, to);

	if (ret > 0)

		file_accessed(filp);

		file_accessed(iocb->ki_filp);

	return ret;

}
@@ -426,7 +433,7 @@ static inline bool pipe_writable(const struct pipe_inode_info *pipe) 
}



static ssize_t

pipe_write(struct kiocb *iocb, struct iov_iter *from)

anon_pipe_write(struct kiocb *iocb, struct iov_iter *from)

{

	struct file *filp = iocb->ki_filp;

	struct pipe_inode_info *pipe = filp->private_data;
@@ -604,12 +611,22 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) 
	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);

	if (wake_next_writer)

		wake_up_interruptible_sync_poll(&pipe->wr_wait, EPOLLOUT | EPOLLWRNORM);

	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {

	return ret;

}



static ssize_t

fifo_pipe_write(struct kiocb *iocb, struct iov_iter *from)

{

	int ret = anon_pipe_write(iocb, from);

	if (ret > 0) {

		struct file *filp = iocb->ki_filp;

		if (sb_start_write_trylock(file_inode(filp)->i_sb)) {

			int err = file_update_time(filp);

			if (err)

				ret = err;

			sb_end_write(file_inode(filp)->i_sb);

		}

	}

	return ret;

}
@@ -1234,8 +1251,8 @@ static int fifo_open(struct inode *inode, struct file *filp) 


const struct file_operations pipefifo_fops = {

	.open		= fifo_open,

	.read_iter	= pipe_read,

	.write_iter	= pipe_write,

	.read_iter	= fifo_pipe_read,

	.write_iter	= fifo_pipe_write,

	.poll		= pipe_poll,

	.unlocked_ioctl	= pipe_ioctl,

	.release	= pipe_release,
@@ -1245,8 +1262,8 @@ const struct file_operations pipefifo_fops = { 


static const struct file_operations pipeanon_fops = {

	.open		= fifo_open,

	.read_iter	= pipe_read,

	.write_iter	= pipe_write,

	.read_iter	= anon_pipe_read,

	.write_iter	= anon_pipe_write,

	.poll		= pipe_poll,

	.unlocked_ioctl	= pipe_ioctl,

	.release	= pipe_release,