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From: Josef Bacik <josef@toxicpanda.com>
To: Nikolay Borisov <nborisov@suse.com>,
	linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 5/9] btrfs: rework btrfs_calc_reclaim_metadata_size
Date: Thu, 1 Oct 2020 17:38:47 -0400	[thread overview]
Message-ID: <bef58ac4-a591-440f-89d7-143449c73ffd@toxicpanda.com> (raw)
In-Reply-To: <812450cb-e21f-83ac-27b3-803000d7b5d5@suse.com>

On 10/1/20 9:59 AM, Nikolay Borisov wrote:
> 
> 
> On 30.09.20 г. 23:01 ч., Josef Bacik wrote:
> <snip>
>>   
>> @@ -800,6 +777,7 @@ static inline int need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
>>   					  u64 used)
>>   {
>>   	u64 thresh = div_factor_fine(space_info->total_bytes, 98);
>> +	u64 to_reclaim, expected;
>>   
>>   	/* If we're just plain full then async reclaim just slows us down. */
>>   	if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh)
>> @@ -812,7 +790,25 @@ static inline int need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
>>   	if (space_info->reclaim_size)
>>   		return 0;
>>   
>> -	if (!btrfs_calc_reclaim_metadata_size(fs_info, space_info))
>> +	to_reclaim = min_t(u64, num_online_cpus() * SZ_1M, SZ_16M);
>> +	if (btrfs_can_overcommit(fs_info, space_info, to_reclaim,
>> +				 BTRFS_RESERVE_FLUSH_ALL))
>> +		return 0;
>> +
>> +	used = btrfs_space_info_used(space_info, true);
>> +	if (btrfs_can_overcommit(fs_info, space_info, SZ_1M,
>> +				 BTRFS_RESERVE_FLUSH_ALL))
>> +		expected = div_factor_fine(space_info->total_bytes, 95);
>> +	else
>> +		expected = div_factor_fine(space_info->total_bytes, 90);
> 
> I think this should be just:
> 
> expected = div_factor_fine(space_info->total_bytes, 90);
> 
> Because before this check we tried to overcommit between 1 and 16m
> (depending on the online CPU's) and we failed. So there is no reason to
> think that :
> 
> btrfs_can_overcommit(fs_info, space_info, SZ_1M, BTRFS_RESERVE_FLUSH_ALL)
> 
> would succeed. So you can simplify the logic by eliminating the 2nd
> check for btrfs_can_overcommit

I remove all this code in a later patch, I'm just moving it here to simplify 
btrfs_calc_reclaim_metadata_size, and then changing this logic later so the 
changes are discrete.

> 
>> +
>> +	if (used > expected)
>> +		to_reclaim = used - expected;
>> +	else
>> +		to_reclaim = 0;
>> +	to_reclaim = min(to_reclaim, space_info->bytes_may_use +
>> +				     space_info->bytes_reserved);
>> +	if (!to_reclaim)
>>   		return 0;
>>   
>>   	return (used >= thresh && !btrfs_fs_closing(fs_info) &&
>>
> 
> nit: Not directly related to your patch but since you are moving the
> code does it make sense to keep the fs_closing and STATE_REMOUNTING
> checks around?
> 

It does because we use this as the breaking condition for the preemptive flusher 
thread.  Thanks,

Josef

  reply	other threads:[~2020-10-01 21:38 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-30 20:01 [PATCH 0/9] Improve preemptive ENOSPC flushing Josef Bacik
2020-09-30 20:01 ` [PATCH 1/9] btrfs: add a trace point for reserve tickets Josef Bacik
2020-10-01  5:54   ` Nikolay Borisov
2020-10-01 21:33     ` Josef Bacik
2020-09-30 20:01 ` [PATCH 2/9] btrfs: improve preemptive background space flushing Josef Bacik
2020-10-01 13:19   ` Nikolay Borisov
2020-10-01 21:35     ` Josef Bacik
2020-09-30 20:01 ` [PATCH 3/9] btrfs: rename need_do_async_reclaim Josef Bacik
2020-10-01 13:20   ` Nikolay Borisov
2020-10-01 13:24   ` Nikolay Borisov
2020-10-01 21:37     ` Josef Bacik
2020-09-30 20:01 ` [PATCH 4/9] btrfs: check reclaim_size in need_preemptive_reclaim Josef Bacik
2020-10-01 13:23   ` Nikolay Borisov
2020-10-01 21:36     ` Josef Bacik
2020-09-30 20:01 ` [PATCH 5/9] btrfs: rework btrfs_calc_reclaim_metadata_size Josef Bacik
2020-10-01 13:59   ` Nikolay Borisov
2020-10-01 21:38     ` Josef Bacik [this message]
2020-09-30 20:01 ` [PATCH 6/9] btrfs: simplify the logic in need_preemptive_flushing Josef Bacik
2020-10-01 14:09   ` Nikolay Borisov
2020-10-01 21:40     ` Josef Bacik
2020-10-02  7:13   ` Nikolay Borisov
2020-09-30 20:01 ` [PATCH 7/9] btrfs: implement space clamping for preemptive flushing Josef Bacik
2020-10-01 14:49   ` Nikolay Borisov
2020-10-01 21:41     ` Josef Bacik
2020-09-30 20:01 ` [PATCH 8/9] btrfs: adjust the flush trace point to include the source Josef Bacik
2020-10-01 15:32   ` Nikolay Borisov
2020-09-30 20:01 ` [PATCH 9/9] btrfs: add a trace class for dumping the current ENOSPC state Josef Bacik
2020-10-02  8:30   ` Nikolay Borisov
2020-10-02 13:45     ` Josef Bacik
2020-10-06 12:55 ` [PATCH 0/9] Improve preemptive ENOSPC flushing Nikolay Borisov

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