* [PATCH 0/3] migration/ram: Some modifications about ram_save_host_page()
@ 2021-02-23 2:16 Kunkun Jiang
2021-02-23 2:16 ` [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page() Kunkun Jiang
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Kunkun Jiang @ 2021-02-23 2:16 UTC (permalink / raw)
To: Juan Quintela, Dr . David Alan Gilbert, open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
Hi,
This series include patches as below:
Patch 1-2:
- modified the comment and code of ram_save_host_page() to make them match each other
Patch 3:
- optimized ram_save_host_page() by using migration_bitmap_find_dirty() to find dirty
pages
Best Regards
Kunkun Jiang
Kunkun Jiang (3):
migration/ram: Modify the code comment of ram_save_host_page()
migration/ram: Modify ram_save_host_page() to match the comment
migration/ram: Optimize ram_save_host_page()
migration/ram.c | 35 ++++++++++++++++++++---------------
1 file changed, 20 insertions(+), 15 deletions(-)
--
2.23.0
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page()
2021-02-23 2:16 [PATCH 0/3] migration/ram: Some modifications about ram_save_host_page() Kunkun Jiang
@ 2021-02-23 2:16 ` Kunkun Jiang
2021-02-24 22:53 ` David Edmondson
2021-02-23 2:16 ` [PATCH 2/3] migration/ram: Modify ram_save_host_page() to match the comment Kunkun Jiang
2021-02-23 2:16 ` [PATCH 3/3] migration/ram: Optimize ram_save_host_page() Kunkun Jiang
2 siblings, 1 reply; 8+ messages in thread
From: Kunkun Jiang @ 2021-02-23 2:16 UTC (permalink / raw)
To: Juan Quintela, Dr . David Alan Gilbert, open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
The ram_save_host_page() has been modified several times
since its birth. But the comment hasn't been modified as it should
be. It'd better to modify the comment to explain ram_save_host_page()
more clearly.
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
---
migration/ram.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 72143da0ac..fc49c3f898 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1970,15 +1970,16 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
}
/**
- * ram_save_host_page: save a whole host page
+ * ram_save_host_page: save a whole host page or the rest of a block
*
- * Starting at *offset send pages up to the end of the current host
- * page. It's valid for the initial offset to point into the middle of
- * a host page in which case the remainder of the hostpage is sent.
- * Only dirty target pages are sent. Note that the host page size may
- * be a huge page for this block.
- * The saving stops at the boundary of the used_length of the block
- * if the RAMBlock isn't a multiple of the host page size.
+ * Starting at pss->page send pages up to the end of the current host
+ * page or the boundary of used_length of the block (if the RAMBlock
+ * isn't a multiple of the host page size). The min one is selected.
+ * Only dirty target pages are sent.
+ *
+ * Note that the host page size may be a huge page for this block, it's
+ * valid for the initial offset to point into the middle of a host page
+ * in which case the remainder of the hostpage is sent.
*
* Returns the number of pages written or negative on error
*
--
2.23.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 2/3] migration/ram: Modify ram_save_host_page() to match the comment
2021-02-23 2:16 [PATCH 0/3] migration/ram: Some modifications about ram_save_host_page() Kunkun Jiang
2021-02-23 2:16 ` [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page() Kunkun Jiang
@ 2021-02-23 2:16 ` Kunkun Jiang
2021-02-23 2:16 ` [PATCH 3/3] migration/ram: Optimize ram_save_host_page() Kunkun Jiang
2 siblings, 0 replies; 8+ messages in thread
From: Kunkun Jiang @ 2021-02-23 2:16 UTC (permalink / raw)
To: Juan Quintela, Dr . David Alan Gilbert, open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
According to the comment, when the host page is a huge page, the
migration_rate_limit() should be executed. If not, this function
can be omitted to save time.
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
---
migration/ram.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/migration/ram.c b/migration/ram.c
index fc49c3f898..c7e18dc2fc 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2017,7 +2017,9 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
pages += tmppages;
pss->page++;
/* Allow rate limiting to happen in the middle of huge pages */
- migration_rate_limit();
+ if (pagesize_bits > 1) {
+ migration_rate_limit();
+ }
} while ((pss->page & (pagesize_bits - 1)) &&
offset_in_ramblock(pss->block,
((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
--
2.23.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 3/3] migration/ram: Optimize ram_save_host_page()
2021-02-23 2:16 [PATCH 0/3] migration/ram: Some modifications about ram_save_host_page() Kunkun Jiang
2021-02-23 2:16 ` [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page() Kunkun Jiang
2021-02-23 2:16 ` [PATCH 2/3] migration/ram: Modify ram_save_host_page() to match the comment Kunkun Jiang
@ 2021-02-23 2:16 ` Kunkun Jiang
2021-02-25 12:48 ` David Edmondson
2 siblings, 1 reply; 8+ messages in thread
From: Kunkun Jiang @ 2021-02-23 2:16 UTC (permalink / raw)
To: Juan Quintela, Dr . David Alan Gilbert, open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
Starting from pss->page, ram_save_host_page() will check every page
and send the dirty pages up to the end of the current host page or
the boundary of used_length of the block. If the host page size is
a huge page, the step "check" will take a lot of time.
This will improve performance to use migration_bitmap_find_dirty().
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
---
migration/ram.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index c7e18dc2fc..c7a2350198 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
int tmppages, pages = 0;
size_t pagesize_bits =
qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
+ unsigned long hostpage_boundary =
+ QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
unsigned long start_page = pss->page;
int res;
@@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
do {
/* Check the pages is dirty and if it is send it */
if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
- pss->page++;
- continue;
+ goto find_next;
}
tmppages = ram_save_target_page(rs, pss, last_stage);
@@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
}
pages += tmppages;
- pss->page++;
/* Allow rate limiting to happen in the middle of huge pages */
if (pagesize_bits > 1) {
migration_rate_limit();
}
- } while ((pss->page & (pagesize_bits - 1)) &&
+find_next:
+ pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
+ } while ((pss->page < hostpage_boundary) &&
offset_in_ramblock(pss->block,
((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
- /* The offset we leave with is the last one we looked at */
- pss->page--;
+ /* The offset we leave with is the min boundary of host page and block */
+ pss->page = MIN(pss->page, hostpage_boundary) - 1;
res = ram_save_release_protection(rs, pss, start_page);
return (res < 0 ? res : pages);
--
2.23.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page()
2021-02-23 2:16 ` [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page() Kunkun Jiang
@ 2021-02-24 22:53 ` David Edmondson
2021-02-25 8:16 ` Kunkun Jiang
0 siblings, 1 reply; 8+ messages in thread
From: David Edmondson @ 2021-02-24 22:53 UTC (permalink / raw)
To: Kunkun Jiang, Juan Quintela, Dr . David Alan Gilbert,
open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
On Tuesday, 2021-02-23 at 10:16:43 +08, Kunkun Jiang wrote:
> The ram_save_host_page() has been modified several times
> since its birth. But the comment hasn't been modified as it should
> be. It'd better to modify the comment to explain ram_save_host_page()
> more clearly.
>
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> ---
> migration/ram.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 72143da0ac..fc49c3f898 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1970,15 +1970,16 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
> }
>
> /**
> - * ram_save_host_page: save a whole host page
> + * ram_save_host_page: save a whole host page or the rest of a block
> *
> - * Starting at *offset send pages up to the end of the current host
> - * page. It's valid for the initial offset to point into the middle of
> - * a host page in which case the remainder of the hostpage is sent.
> - * Only dirty target pages are sent. Note that the host page size may
> - * be a huge page for this block.
> - * The saving stops at the boundary of the used_length of the block
> - * if the RAMBlock isn't a multiple of the host page size.
> + * Starting at pss->page send pages up to the end of the current host
> + * page or the boundary of used_length of the block (if the RAMBlock
> + * isn't a multiple of the host page size). The min one is selected.
> + * Only dirty target pages are sent.
> + *
> + * Note that the host page size may be a huge page for this block, it's
> + * valid for the initial offset to point into the middle of a host page
> + * in which case the remainder of the hostpage is sent.
How about:
* Send dirty pages between pss->page and either the end of that page or
* the used_length of the RAMBlock, whichever is smaller.
*
* Note that if the host page is a huge page, pss->page may be in the
* middle of that page.
> *
> * Returns the number of pages written or negative on error
> *
> --
> 2.23.0
dme.
--
I'm in with the in crowd, I know every latest dance.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page()
2021-02-24 22:53 ` David Edmondson
@ 2021-02-25 8:16 ` Kunkun Jiang
0 siblings, 0 replies; 8+ messages in thread
From: Kunkun Jiang @ 2021-02-25 8:16 UTC (permalink / raw)
To: David Edmondson, Juan Quintela, Dr . David Alan Gilbert,
open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
On 2021/2/25 6:53, David Edmondson wrote:
> On Tuesday, 2021-02-23 at 10:16:43 +08, Kunkun Jiang wrote:
>
>> The ram_save_host_page() has been modified several times
>> since its birth. But the comment hasn't been modified as it should
>> be. It'd better to modify the comment to explain ram_save_host_page()
>> more clearly.
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
>> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
>> ---
>> migration/ram.c | 17 +++++++++--------
>> 1 file changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 72143da0ac..fc49c3f898 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -1970,15 +1970,16 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>> }
>>
>> /**
>> - * ram_save_host_page: save a whole host page
>> + * ram_save_host_page: save a whole host page or the rest of a block
>> *
>> - * Starting at *offset send pages up to the end of the current host
>> - * page. It's valid for the initial offset to point into the middle of
>> - * a host page in which case the remainder of the hostpage is sent.
>> - * Only dirty target pages are sent. Note that the host page size may
>> - * be a huge page for this block.
>> - * The saving stops at the boundary of the used_length of the block
>> - * if the RAMBlock isn't a multiple of the host page size.
>> + * Starting at pss->page send pages up to the end of the current host
>> + * page or the boundary of used_length of the block (if the RAMBlock
>> + * isn't a multiple of the host page size). The min one is selected.
>> + * Only dirty target pages are sent.
>> + *
>> + * Note that the host page size may be a huge page for this block, it's
>> + * valid for the initial offset to point into the middle of a host page
>> + * in which case the remainder of the hostpage is sent.
> How about:
>
> * Send dirty pages between pss->page and either the end of that page or
> * the used_length of the RAMBlock, whichever is smaller.
> *
> * Note that if the host page is a huge page, pss->page may be in the
> * middle of that page.
Thank you. It looks concise and comprehensive.
Best Regards
Kunkun Jiang
>> *
>> * Returns the number of pages written or negative on error
>> *
>> --
>> 2.23.0
> dme.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 3/3] migration/ram: Optimize ram_save_host_page()
2021-02-23 2:16 ` [PATCH 3/3] migration/ram: Optimize ram_save_host_page() Kunkun Jiang
@ 2021-02-25 12:48 ` David Edmondson
2021-03-01 7:33 ` Kunkun Jiang
0 siblings, 1 reply; 8+ messages in thread
From: David Edmondson @ 2021-02-25 12:48 UTC (permalink / raw)
To: Kunkun Jiang, Juan Quintela, Dr . David Alan Gilbert,
open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
On Tuesday, 2021-02-23 at 10:16:45 +08, Kunkun Jiang wrote:
> Starting from pss->page, ram_save_host_page() will check every page
> and send the dirty pages up to the end of the current host page or
> the boundary of used_length of the block. If the host page size is
> a huge page, the step "check" will take a lot of time.
>
> This will improve performance to use migration_bitmap_find_dirty().
>
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
> ---
> migration/ram.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index c7e18dc2fc..c7a2350198 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
> int tmppages, pages = 0;
> size_t pagesize_bits =
> qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
> + unsigned long hostpage_boundary =
> + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
> unsigned long start_page = pss->page;
> int res;
>
> @@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
> do {
> /* Check the pages is dirty and if it is send it */
> if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
> - pss->page++;
> - continue;
> + goto find_next;
> }
>
> tmppages = ram_save_target_page(rs, pss, last_stage);
> @@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
> }
>
> pages += tmppages;
> - pss->page++;
> /* Allow rate limiting to happen in the middle of huge pages */
> if (pagesize_bits > 1) {
> migration_rate_limit();
> }
> - } while ((pss->page & (pagesize_bits - 1)) &&
> +find_next:
> + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
> + } while ((pss->page < hostpage_boundary) &&
> offset_in_ramblock(pss->block,
> ((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
This ends up looking very messy, with a goto inside the loop.
Wouldn't it be cleaner to invert the sense of the
migration_bitmap_clear_dirty() test, such that
migration_bitmap_find_dirty() is called after the body of the test?
> - /* The offset we leave with is the last one we looked at */
> - pss->page--;
> + /* The offset we leave with is the min boundary of host page and block */
> + pss->page = MIN(pss->page, hostpage_boundary) - 1;
>
> res = ram_save_release_protection(rs, pss, start_page);
> return (res < 0 ? res : pages);
> --
> 2.23.0
dme.
--
Oliver darling, call Mister Haney, I think our speakers are blown.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 3/3] migration/ram: Optimize ram_save_host_page()
2021-02-25 12:48 ` David Edmondson
@ 2021-03-01 7:33 ` Kunkun Jiang
0 siblings, 0 replies; 8+ messages in thread
From: Kunkun Jiang @ 2021-03-01 7:33 UTC (permalink / raw)
To: David Edmondson, Juan Quintela, Dr . David Alan Gilbert,
open list:All patches CC here
Cc: Zenghui Yu, wanghaibin.wang, Keqian Zhu
On 2021/2/25 20:48, David Edmondson wrote:
> On Tuesday, 2021-02-23 at 10:16:45 +08, Kunkun Jiang wrote:
>
>> Starting from pss->page, ram_save_host_page() will check every page
>> and send the dirty pages up to the end of the current host page or
>> the boundary of used_length of the block. If the host page size is
>> a huge page, the step "check" will take a lot of time.
>>
>> This will improve performance to use migration_bitmap_find_dirty().
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
>> Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
>> ---
>> migration/ram.c | 14 ++++++++------
>> 1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/migration/ram.c b/migration/ram.c
>> index c7e18dc2fc..c7a2350198 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -1994,6 +1994,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
>> int tmppages, pages = 0;
>> size_t pagesize_bits =
>> qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
>> + unsigned long hostpage_boundary =
>> + QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
>> unsigned long start_page = pss->page;
>> int res;
>>
>> @@ -2005,8 +2007,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
>> do {
>> /* Check the pages is dirty and if it is send it */
>> if (!migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
>> - pss->page++;
>> - continue;
>> + goto find_next;
>> }
>>
>> tmppages = ram_save_target_page(rs, pss, last_stage);
>> @@ -2015,16 +2016,17 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
>> }
>>
>> pages += tmppages;
>> - pss->page++;
>> /* Allow rate limiting to happen in the middle of huge pages */
>> if (pagesize_bits > 1) {
>> migration_rate_limit();
>> }
>> - } while ((pss->page & (pagesize_bits - 1)) &&
>> +find_next:
>> + pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
>> + } while ((pss->page < hostpage_boundary) &&
>> offset_in_ramblock(pss->block,
>> ((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
> This ends up looking very messy, with a goto inside the loop.
>
> Wouldn't it be cleaner to invert the sense of the
> migration_bitmap_clear_dirty() test, such that
> migration_bitmap_find_dirty() is called after the body of the test?
Sorry for the late reply.
Thanks for your advice. I will post a v2 as soon as possible.
Best Regards.
Kunkun Jiang
>> - /* The offset we leave with is the last one we looked at */
>> - pss->page--;
>> + /* The offset we leave with is the min boundary of host page and block */
>> + pss->page = MIN(pss->page, hostpage_boundary) - 1;
>>
>> res = ram_save_release_protection(rs, pss, start_page);
>> return (res < 0 ? res : pages);
>> --
>> 2.23.0
> dme.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2021-03-01 7:35 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-02-23 2:16 [PATCH 0/3] migration/ram: Some modifications about ram_save_host_page() Kunkun Jiang
2021-02-23 2:16 ` [PATCH 1/3] migration/ram: Modify the code comment of ram_save_host_page() Kunkun Jiang
2021-02-24 22:53 ` David Edmondson
2021-02-25 8:16 ` Kunkun Jiang
2021-02-23 2:16 ` [PATCH 2/3] migration/ram: Modify ram_save_host_page() to match the comment Kunkun Jiang
2021-02-23 2:16 ` [PATCH 3/3] migration/ram: Optimize ram_save_host_page() Kunkun Jiang
2021-02-25 12:48 ` David Edmondson
2021-03-01 7:33 ` Kunkun Jiang
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