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btrfs-progs: send: increase size of transfer buffer 

4K is quite small, increase it to 64K. This reduces number of
context switches and calls to read. Kernel sends us about 50K of data
per read, so increasing the buffer further does not make any
improvement.

Example run on tests/cli-tests/004-send-parent-multi-subvol:
4K:
  - ~800 context switches
  - ~5000 calls to read

64K:
  - ~450 context switches
  - ~500 calls to read

Signed-off-by: David Sterba <dsterba@suse.com>
master
David Sterba 2016-11-02 13:27:45 +01:00
parent 88edac358c
commit 76fc07e3a6
1 changed files with 3 additions and 1 deletions
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4
cmds-send.c
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@ -44,6 +44,8 @@
#include "send.h"
#include "send-utils.h"
#define SEND_BUFFER_SIZE (64 * 1024)
/*
* Default is 1 for historical reasons, changing may break scripts that expect
* the 'At subvol' message.
@ -222,7 +224,7 @@ static void *dump_thread(void *arg_)
{
int ret;
struct btrfs_send *s = (struct btrfs_send*)arg_;
char buf[4096];
char buf[SEND_BUFFER_SIZE];
int readed;
while (1) {