Re: remove mixture of non-atomic operations with page->flags which requires atomic operations to access

[William Lee Irwin III <wli@holomorphy.com>]

On Sun, 2 Jun 2002, William Lee Irwin III wrote:
>> page->flags is effectively a lock word as its various bits are updatable
>> and accessible only by atomic operations. This patch removes the update
>> of page->flags in __free_pages_ok() with non-atomic operations in favor
>> of using atomic bit operations to update the bits to be cleared.
>>  	ClearPageDirty(page);
>> -	page->flags &= ~(1<<PG_referenced);
>> +	ClearPageUptodate(page);
>> +	ClearPageSlab(page);
>> +	ClearPageNosave(page);
>> +	ClearPageChecked(page);

On Mon, Jun 03, 2002 at 11:14:43AM +0100, Hugh Dickins wrote:
> Don't all those atomic volatile bitops slow down a hotpath for no real
> gain?  I'm all for clearing all possible flag bits at that point, but
> would prefer just one mask myself.  But given all the preceding tests,
> and the ClearPageDirty, perhaps I'm foolish to question your additions.
> And wasn't it originally clearing the referenced bit, now leaving it?
> Hugh

It should be clearing it, I'd retransmit if there weren't other objections
to address...


Cheers,
Bill