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Improve the discard-window write strategy

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Now flush the window before discarding it in the previous
loop, following exactly the Linus advices.
This commit is contained in:
Andrea Mazzoleni 2016-09-09 19:52:39 +02:00
parent b5e5a0791b
commit 7d65eb83b1
1 changed files with 62 additions and 26 deletions
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88
cmdline/support.c
View file

@ -932,15 +932,21 @@ int advise_open(struct advise_struct* advise, int f)
int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_off_t size)
{
data_off_t handle_offset;
data_off_t handle_size;
data_off_t flush_offset;
data_off_t flush_size;
data_off_t discard_offset;
data_off_t discard_size;
(void)f;
(void)handle_offset;
(void)handle_size;
(void)flush_offset;
(void)flush_size;
(void)discard_offset;
(void)discard_size;
handle_offset = 0;
handle_size = 0;
flush_offset = 0;
flush_size = 0;
discard_offset = 0;
discard_size = 0;
/*
* Follow Linus recommendations about fast writes.
@ -995,12 +1001,41 @@ int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_of
* ---
*/
if (advise->mode == ADVISE_FLUSH || advise->mode == ADVISE_DISCARD) {
handle_offset = offset;
handle_size = size;
}
switch (advise->mode) {
case ADVISE_FLUSH :
flush_offset = offset;
flush_size = size;
break;
case ADVISE_DISCARD :
discard_offset = offset;
discard_size = size;
break;
case ADVISE_FLUSH_WINDOW :
/* if the dirty range can be extended */
if (advise->dirty_end == offset) {
/* extent the dirty range */
advise->dirty_end += size;
if (advise->mode == ADVISE_FLUSH_WINDOW || advise->mode == ADVISE_DISCARD_WINDOW) {
/* if we reached the window size */
if (advise->dirty_end - advise->dirty_begin >= ADVISE_WINDOW_SIZE) {
/* flush the window */
flush_offset = advise->dirty_begin;
flush_size = ADVISE_WINDOW_SIZE;
/* remove it from the dirty range */
advise->dirty_begin += ADVISE_WINDOW_SIZE;
}
} else {
/* otherwise flush the existing dirty */
flush_offset = advise->dirty_begin;
flush_size = advise->dirty_end - advise->dirty_begin;
/* and set the new range as dirty */
advise->dirty_begin = offset;
advise->dirty_end = offset + size;
}
break;
case ADVISE_DISCARD_WINDOW :
/* if the dirty range can be extended */
if (advise->dirty_end == offset) {
/* extent the dirty range */
@ -1008,32 +1043,35 @@ int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_of
/* if we reached the double window size */
if (advise->dirty_end - advise->dirty_begin >= 2 * ADVISE_WINDOW_SIZE) {
/* handle the first window */
handle_offset = advise->dirty_begin;
handle_size = ADVISE_WINDOW_SIZE;
/* discard the first window */
discard_offset = advise->dirty_begin;
discard_size = ADVISE_WINDOW_SIZE;
/* remove it from the dirty range */
advise->dirty_begin += ADVISE_WINDOW_SIZE;
/* flush the second window */
flush_offset = advise->dirty_begin;
flush_size = ADVISE_WINDOW_SIZE;
}
} else {
/* otherwise flush the existing dirty */
handle_offset = advise->dirty_begin;
handle_size = advise->dirty_end - advise->dirty_begin;
/* otherwise discard the existing dirty */
discard_offset = advise->dirty_begin;
discard_size = advise->dirty_end - advise->dirty_begin;
/* and set the new range as dirty */
advise->dirty_begin = offset;
advise->dirty_end = offset + size;
}
break;
}
#if HAVE_SYNC_FILE_RANGE
if ((advise->mode == ADVISE_FLUSH || advise->mode == ADVISE_FLUSH_WINDOW)
&& handle_size != 0
) {
if (flush_size != 0) {
int ret;
/* start writing immediately */
ret = sync_file_range(f, handle_offset, handle_size, SYNC_FILE_RANGE_WRITE);
ret = sync_file_range(f, flush_offset, flush_size, SYNC_FILE_RANGE_WRITE);
if (ret != 0) {
/* LCOV_EXCL_START */
return -1;
@ -1043,13 +1081,11 @@ int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_of
#endif
#if HAVE_SYNC_FILE_RANGE && HAVE_POSIX_FADVISE
if ((advise->mode == ADVISE_DISCARD || advise->mode == ADVISE_DISCARD_WINDOW)
&& handle_size != 0
) {
if (discard_size != 0) {
int ret;
/* send the data to the disk and wait until it's written */
ret = sync_file_range(f, handle_offset, handle_size, SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE | SYNC_FILE_RANGE_WAIT_AFTER);
ret = sync_file_range(f, discard_offset, discard_size, SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE | SYNC_FILE_RANGE_WAIT_AFTER);
if (ret != 0) {
/* LCOV_EXCL_START */
return -1;
@ -1057,7 +1093,7 @@ int advise_write(struct advise_struct* advise, int f, data_off_t offset, data_of
}
/* flush the data from the cache */
ret = posix_fadvise(f, handle_offset, handle_size, POSIX_FADV_DONTNEED);
ret = posix_fadvise(f, discard_offset, discard_size, POSIX_FADV_DONTNEED);
if (ret != 0) {
/* LCOV_EXCL_START */
errno = ret; /* posix_fadvise return the error code */