* [PATCH] fs/buffer: simplify the code flow of LRU management algorithm
@ 2015-09-10 8:09 Minfei Huang
2015-09-28 5:36 ` Minfei Huang
0 siblings, 1 reply; 4+ messages in thread
From: Minfei Huang @ 2015-09-10 8:09 UTC (permalink / raw)
To: viro; +Cc: linux-fsdevel, linux-kernel, mhuang, Minfei Huang
From: Minfei Huang <mnfhuang@gmail.com>
There is a buffer_head lru list cache in local cpu to accelerate the
speed. The LRU management algorithm is simple enough in
bh_lru_install().
There are three situtaions we should deal with.
1) All/part of the lru cache is NULL.
2) The new buffer_head hitts the lru cache.
3) The new buffer_head does hit the lru cache.
We put the new buffer_head at the head of lru cache, then copy the
buffer_head from the original lru cache, and drop the spare.
Signed-off-by: Minfei Huang <mnfhuang@gmail.com>
---
fs/buffer.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 1cf7a53..2139574 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1287,8 +1287,6 @@ static inline void check_irqs_on(void)
*/
static void bh_lru_install(struct buffer_head *bh)
{
- struct buffer_head *evictee = NULL;
-
check_irqs_on();
bh_lru_lock();
if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
@@ -1302,25 +1300,35 @@ static void bh_lru_install(struct buffer_head *bh)
struct buffer_head *bh2 =
__this_cpu_read(bh_lrus.bhs[in]);
- if (bh2 == bh) {
+ if (bh2 == NULL) {
+ /* Rest value in bh_lrus.bhs always is NULL */
+ break;
+ } else if (bh2 == bh) {
__brelse(bh2);
} else {
- if (out >= BH_LRU_SIZE) {
- BUG_ON(evictee != NULL);
- evictee = bh2;
+ if (out == BH_LRU_SIZE) {
+ /*
+ * this condition will be happened,
+ * only if none of entry in
+ * bh_lrus.bhs hits the new bh,
+ * so the last bh should be released.
+ */
+ BUG_ON(in != BH_LRU_SIZE - 1);
+ __brelse(bh2);
+ break;
} else {
bhs[out++] = bh2;
}
}
}
- while (out < BH_LRU_SIZE)
- bhs[out++] = NULL;
- memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
+ /*
+ * it is fine that the value out may be smaller than
+ * BH_LRU_SIZE. The rest of the value in bh_lrus.bhs is NULL.
+ */
+ memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs,
+ sizeof(struct buffer_head *) * out);
}
bh_lru_unlock();
-
- if (evictee)
- __brelse(evictee);
}
/*
--
2.1.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] fs/buffer: simplify the code flow of LRU management algorithm
2015-09-10 8:09 [PATCH] fs/buffer: simplify the code flow of LRU management algorithm Minfei Huang
@ 2015-09-28 5:36 ` Minfei Huang
2015-09-28 6:52 ` yalin wang
0 siblings, 1 reply; 4+ messages in thread
From: Minfei Huang @ 2015-09-28 5:36 UTC (permalink / raw)
To: viro; +Cc: linux-fsdevel, linux-kernel, Minfei Huang
Ping, Could you someone help to review this patch?
Thanks
Minfei
On 09/10/15 at 04:09pm, Minfei Huang wrote:
> From: Minfei Huang <mnfhuang@gmail.com>
>
> There is a buffer_head lru list cache in local cpu to accelerate the
> speed. The LRU management algorithm is simple enough in
> bh_lru_install().
>
> There are three situtaions we should deal with.
> 1) All/part of the lru cache is NULL.
> 2) The new buffer_head hitts the lru cache.
> 3) The new buffer_head does hit the lru cache.
>
> We put the new buffer_head at the head of lru cache, then copy the
> buffer_head from the original lru cache, and drop the spare.
>
> Signed-off-by: Minfei Huang <mnfhuang@gmail.com>
> ---
> fs/buffer.c | 32 ++++++++++++++++++++------------
> 1 file changed, 20 insertions(+), 12 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 1cf7a53..2139574 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1287,8 +1287,6 @@ static inline void check_irqs_on(void)
> */
> static void bh_lru_install(struct buffer_head *bh)
> {
> - struct buffer_head *evictee = NULL;
> -
> check_irqs_on();
> bh_lru_lock();
> if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
> @@ -1302,25 +1300,35 @@ static void bh_lru_install(struct buffer_head *bh)
> struct buffer_head *bh2 =
> __this_cpu_read(bh_lrus.bhs[in]);
>
> - if (bh2 == bh) {
> + if (bh2 == NULL) {
> + /* Rest value in bh_lrus.bhs always is NULL */
> + break;
> + } else if (bh2 == bh) {
> __brelse(bh2);
> } else {
> - if (out >= BH_LRU_SIZE) {
> - BUG_ON(evictee != NULL);
> - evictee = bh2;
> + if (out == BH_LRU_SIZE) {
> + /*
> + * this condition will be happened,
> + * only if none of entry in
> + * bh_lrus.bhs hits the new bh,
> + * so the last bh should be released.
> + */
> + BUG_ON(in != BH_LRU_SIZE - 1);
> + __brelse(bh2);
> + break;
> } else {
> bhs[out++] = bh2;
> }
> }
> }
> - while (out < BH_LRU_SIZE)
> - bhs[out++] = NULL;
> - memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
> + /*
> + * it is fine that the value out may be smaller than
> + * BH_LRU_SIZE. The rest of the value in bh_lrus.bhs is NULL.
> + */
> + memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs,
> + sizeof(struct buffer_head *) * out);
> }
> bh_lru_unlock();
> -
> - if (evictee)
> - __brelse(evictee);
> }
>
> /*
> --
> 2.1.0
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] fs/buffer: simplify the code flow of LRU management algorithm
2015-09-28 5:36 ` Minfei Huang
@ 2015-09-28 6:52 ` yalin wang
2015-10-09 16:18 ` Minfei Huang
0 siblings, 1 reply; 4+ messages in thread
From: yalin wang @ 2015-09-28 6:52 UTC (permalink / raw)
To: Minfei Huang; +Cc: Al Viro, linux-fsdevel, linux-kernel, Minfei Huang
why not change like this:
diff --git a/fs/buffer.c b/fs/buffer.c
index 82283ab..d6769f1 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1287,40 +1287,31 @@ static inline void check_irqs_on(void)
*/
static void bh_lru_install(struct buffer_head *bh)
{
- struct buffer_head *evictee = NULL;
+ struct buffer_head *old = NULL;
check_irqs_on();
bh_lru_lock();
if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
- struct buffer_head *bhs[BH_LRU_SIZE];
- int in;
+ struct buffer_head *temp;
int out = 0;
+ old = __this_cpu_read(bh_lrus.bhs[0]);
get_bh(bh);
- bhs[out++] = bh;
- for (in = 0; in < BH_LRU_SIZE; in++) {
- struct buffer_head *bh2 =
- __this_cpu_read(bh_lrus.bhs[in]);
-
- if (bh2 == bh) {
- __brelse(bh2);
+ __this_cpu_write(bh_lrus.bhs[out++], bh);
+ for (; out < BH_LRU_SIZE; out++) {
+ if (old == bh || old == NULL) {
+ break;
} else {
- if (out >= BH_LRU_SIZE) {
- BUG_ON(evictee != NULL);
- evictee = bh2;
- } else {
- bhs[out++] = bh2;
- }
+ temp = __this_cpu_read(bh_lrus.bhs[out]);
+ __this_cpu_write(bh_lrus.bhs[out], old);
+ old = temp;
}
}
- while (out < BH_LRU_SIZE)
- bhs[out++] = NULL;
- memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
}
bh_lru_unlock();
- if (evictee)
- __brelse(evictee);
+ if (old)
+ __brelse(old);
}
/*
more simple to understand and have better performance .
am i understanding correctly ?
> On Sep 28, 2015, at 13:36, Minfei Huang <mhuang@redhat.com> wrote:
>
> Ping, Could you someone help to review this patch?
>
> Thanks
> Minfei
>
> On 09/10/15 at 04:09pm, Minfei Huang wrote:
>> From: Minfei Huang <mnfhuang@gmail.com>
>>
>> There is a buffer_head lru list cache in local cpu to accelerate the
>> speed. The LRU management algorithm is simple enough in
>> bh_lru_install().
>>
>> There are three situtaions we should deal with.
>> 1) All/part of the lru cache is NULL.
>> 2) The new buffer_head hitts the lru cache.
>> 3) The new buffer_head does hit the lru cache.
>>
>> We put the new buffer_head at the head of lru cache, then copy the
>> buffer_head from the original lru cache, and drop the spare.
>>
>> Signed-off-by: Minfei Huang <mnfhuang@gmail.com>
>> ---
>> fs/buffer.c | 32 ++++++++++++++++++++------------
>> 1 file changed, 20 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/buffer.c b/fs/buffer.c
>> index 1cf7a53..2139574 100644
>> --- a/fs/buffer.c
>> +++ b/fs/buffer.c
>> @@ -1287,8 +1287,6 @@ static inline void check_irqs_on(void)
>> */
>> static void bh_lru_install(struct buffer_head *bh)
>> {
>> - struct buffer_head *evictee = NULL;
>> -
>> check_irqs_on();
>> bh_lru_lock();
>> if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
>> @@ -1302,25 +1300,35 @@ static void bh_lru_install(struct buffer_head *bh)
>> struct buffer_head *bh2 =
>> __this_cpu_read(bh_lrus.bhs[in]);
>>
>> - if (bh2 == bh) {
>> + if (bh2 == NULL) {
>> + /* Rest value in bh_lrus.bhs always is NULL */
>> + break;
>> + } else if (bh2 == bh) {
>> __brelse(bh2);
>> } else {
>> - if (out >= BH_LRU_SIZE) {
>> - BUG_ON(evictee != NULL);
>> - evictee = bh2;
>> + if (out == BH_LRU_SIZE) {
>> + /*
>> + * this condition will be happened,
>> + * only if none of entry in
>> + * bh_lrus.bhs hits the new bh,
>> + * so the last bh should be released.
>> + */
>> + BUG_ON(in != BH_LRU_SIZE - 1);
>> + __brelse(bh2);
>> + break;
>> } else {
>> bhs[out++] = bh2;
>> }
>> }
>> }
>> - while (out < BH_LRU_SIZE)
>> - bhs[out++] = NULL;
>> - memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
>> + /*
>> + * it is fine that the value out may be smaller than
>> + * BH_LRU_SIZE. The rest of the value in bh_lrus.bhs is NULL.
>> + */
>> + memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs,
>> + sizeof(struct buffer_head *) * out);
>> }
>> bh_lru_unlock();
>> -
>> - if (evictee)
>> - __brelse(evictee);
>> }
>>
>> /*
>> --
>> 2.1.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] fs/buffer: simplify the code flow of LRU management algorithm
2015-09-28 6:52 ` yalin wang
@ 2015-10-09 16:18 ` Minfei Huang
0 siblings, 0 replies; 4+ messages in thread
From: Minfei Huang @ 2015-10-09 16:18 UTC (permalink / raw)
To: yalin wang; +Cc: Al Viro, linux-fsdevel, linux-kernel, Minfei Huang
On 09/28/15 at 02:52pm, yalin wang wrote:
> why not change like this:
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 82283ab..d6769f1 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1287,40 +1287,31 @@ static inline void check_irqs_on(void)
> */
> static void bh_lru_install(struct buffer_head *bh)
> {
> - struct buffer_head *evictee = NULL;
> + struct buffer_head *old = NULL;
>
> check_irqs_on();
> bh_lru_lock();
> if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
> - struct buffer_head *bhs[BH_LRU_SIZE];
> - int in;
> + struct buffer_head *temp;
> int out = 0;
>
> + old = __this_cpu_read(bh_lrus.bhs[0]);
> get_bh(bh);
> - bhs[out++] = bh;
> - for (in = 0; in < BH_LRU_SIZE; in++) {
> - struct buffer_head *bh2 =
> - __this_cpu_read(bh_lrus.bhs[in]);
> -
> - if (bh2 == bh) {
> - __brelse(bh2);
> + __this_cpu_write(bh_lrus.bhs[out++], bh);
> + for (; out < BH_LRU_SIZE; out++) {
> + if (old == bh || old == NULL) {
> + break;
> } else {
> - if (out >= BH_LRU_SIZE) {
> - BUG_ON(evictee != NULL);
> - evictee = bh2;
> - } else {
> - bhs[out++] = bh2;
> - }
> + temp = __this_cpu_read(bh_lrus.bhs[out]);
> + __this_cpu_write(bh_lrus.bhs[out], old);
> + old = temp;
If we should copy the successive struct buffer_head, it is appropriate
to use memcpy to copy a bunch of struct buffer_head.
Thanks
Minfei
> }
> }
> - while (out < BH_LRU_SIZE)
> - bhs[out++] = NULL;
> - memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
> }
> bh_lru_unlock();
>
> - if (evictee)
> - __brelse(evictee);
> + if (old)
> + __brelse(old);
> }
>
> /*
>
>
> more simple to understand and have better performance .
> am i understanding correctly ?
>
> > On Sep 28, 2015, at 13:36, Minfei Huang <mhuang@redhat.com> wrote:
> >
> > Ping, Could you someone help to review this patch?
> >
> > Thanks
> > Minfei
> >
> > On 09/10/15 at 04:09pm, Minfei Huang wrote:
> >> From: Minfei Huang <mnfhuang@gmail.com>
> >>
> >> There is a buffer_head lru list cache in local cpu to accelerate the
> >> speed. The LRU management algorithm is simple enough in
> >> bh_lru_install().
> >>
> >> There are three situtaions we should deal with.
> >> 1) All/part of the lru cache is NULL.
> >> 2) The new buffer_head hitts the lru cache.
> >> 3) The new buffer_head does hit the lru cache.
> >>
> >> We put the new buffer_head at the head of lru cache, then copy the
> >> buffer_head from the original lru cache, and drop the spare.
> >>
> >> Signed-off-by: Minfei Huang <mnfhuang@gmail.com>
> >> ---
> >> fs/buffer.c | 32 ++++++++++++++++++++------------
> >> 1 file changed, 20 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/fs/buffer.c b/fs/buffer.c
> >> index 1cf7a53..2139574 100644
> >> --- a/fs/buffer.c
> >> +++ b/fs/buffer.c
> >> @@ -1287,8 +1287,6 @@ static inline void check_irqs_on(void)
> >> */
> >> static void bh_lru_install(struct buffer_head *bh)
> >> {
> >> - struct buffer_head *evictee = NULL;
> >> -
> >> check_irqs_on();
> >> bh_lru_lock();
> >> if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
> >> @@ -1302,25 +1300,35 @@ static void bh_lru_install(struct buffer_head *bh)
> >> struct buffer_head *bh2 =
> >> __this_cpu_read(bh_lrus.bhs[in]);
> >>
> >> - if (bh2 == bh) {
> >> + if (bh2 == NULL) {
> >> + /* Rest value in bh_lrus.bhs always is NULL */
> >> + break;
> >> + } else if (bh2 == bh) {
> >> __brelse(bh2);
> >> } else {
> >> - if (out >= BH_LRU_SIZE) {
> >> - BUG_ON(evictee != NULL);
> >> - evictee = bh2;
> >> + if (out == BH_LRU_SIZE) {
> >> + /*
> >> + * this condition will be happened,
> >> + * only if none of entry in
> >> + * bh_lrus.bhs hits the new bh,
> >> + * so the last bh should be released.
> >> + */
> >> + BUG_ON(in != BH_LRU_SIZE - 1);
> >> + __brelse(bh2);
> >> + break;
> >> } else {
> >> bhs[out++] = bh2;
> >> }
> >> }
> >> }
> >> - while (out < BH_LRU_SIZE)
> >> - bhs[out++] = NULL;
> >> - memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
> >> + /*
> >> + * it is fine that the value out may be smaller than
> >> + * BH_LRU_SIZE. The rest of the value in bh_lrus.bhs is NULL.
> >> + */
> >> + memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs,
> >> + sizeof(struct buffer_head *) * out);
> >> }
> >> bh_lru_unlock();
> >> -
> >> - if (evictee)
> >> - __brelse(evictee);
> >> }
> >>
> >> /*
> >> --
> >> 2.1.0
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >> Please read the FAQ at http://www.tux.org/lkml/
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-09-10 8:09 [PATCH] fs/buffer: simplify the code flow of LRU management algorithm Minfei Huang
2015-09-28 5:36 ` Minfei Huang
2015-09-28 6:52 ` yalin wang
2015-10-09 16:18 ` Minfei Huang
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