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| Started by | Dave Hansen <dave.hansen@intel.com> |
|---|---|
| First post | 2017-07-11 20:30 +0200 |
| Last post | 2017-07-12 04:30 +0200 |
| Articles | 2 — 2 participants |
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Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics Dave Hansen <dave.hansen@intel.com> - 2017-07-11 20:30 +0200
Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics "Huang\, Ying" <ying.huang@intel.com> - 2017-07-12 04:30 +0200
| From | Dave Hansen <dave.hansen@intel.com> |
|---|---|
| Date | 2017-07-11 20:30 +0200 |
| Subject | Re: [PATCH -mm -v2 2/6] mm, swap: Add swap readahead hit statistics |
| Message-ID | <u2854-5KF-21@gated-at.bofh.it> |
On 06/29/2017 06:44 PM, Huang, Ying wrote:
>
> static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
> +static atomic_long_t swapin_readahead_hits_total = ATOMIC_INIT(0);
> +static atomic_long_t swapin_readahead_total = ATOMIC_INIT(0);
>
> void show_swap_cache_info(void)
> {
> @@ -305,8 +307,10 @@ struct page * lookup_swap_cache(swp_entry_t entry)
>
> if (page && likely(!PageTransCompound(page))) {
> INC_CACHE_INFO(find_success);
> - if (TestClearPageReadahead(page))
> + if (TestClearPageReadahead(page)) {
> atomic_inc(&swapin_readahead_hits);
> + atomic_long_inc(&swapin_readahead_hits_total);
> + }
> }
Adding global atomics that we touch in hot paths seems like poor
future-proofing. Are we sure we want to do this and not use some of the
nice, fancy, percpu counters that we have?
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| From | "Huang\, Ying" <ying.huang@intel.com> |
|---|---|
| Date | 2017-07-12 04:30 +0200 |
| Message-ID | <u2fzA-25Y-11@gated-at.bofh.it> |
| In reply to | #1685284 |
Dave Hansen <dave.hansen@intel.com> writes:
> On 06/29/2017 06:44 PM, Huang, Ying wrote:
>>
>> static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
>> +static atomic_long_t swapin_readahead_hits_total = ATOMIC_INIT(0);
>> +static atomic_long_t swapin_readahead_total = ATOMIC_INIT(0);
>>
>> void show_swap_cache_info(void)
>> {
>> @@ -305,8 +307,10 @@ struct page * lookup_swap_cache(swp_entry_t entry)
>>
>> if (page && likely(!PageTransCompound(page))) {
>> INC_CACHE_INFO(find_success);
>> - if (TestClearPageReadahead(page))
>> + if (TestClearPageReadahead(page)) {
>> atomic_inc(&swapin_readahead_hits);
>> + atomic_long_inc(&swapin_readahead_hits_total);
>> + }
>> }
>
> Adding global atomics that we touch in hot paths seems like poor
> future-proofing. Are we sure we want to do this and not use some of the
> nice, fancy, percpu counters that we have?
Yes. It is much better to use percpu counters instead. Will change it
in the next version.
Best Regards,
Huang, Ying
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