From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [rfc patch] drivers/block/zram: Replace bit spinlocks with
 rtmutex for -rt
Date: Wed, 30 Mar 2016 11:19:39 +0200
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References: <1458641979.15742.6.camel@gmail.com>
 <20160330085622.GA21849@linutronix.de> <20160330091302.GB2769@swordfish>
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Cc: Mike Galbraith <umgwanakikbuti@gmail.com>,
	Minchan Kim <minchan@kernel.org>,
	Nitin Gupta <ngupta@vflare.org>,
	RT <linux-rt-users@vger.kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
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On 03/30/2016 11:13 AM, Sergey Senozhatsky wrote:
> On (03/30/16 10:56), Sebastian Andrzej Siewior wrote:
> [..]
>>> +static inline void zram_unlock_table(struct zram_table_entry *table)
>>> +{
>>> +	__clear_bit(ZRAM_ACCESS, &table->value);
>>> +	spin_unlock(&table->lock);
>>> +}
>>
>> ZRAM_ACCESS is the only bit used for locking. ZRAM_ZERO is the only flag
>> set / tested. 
>> Would it be possible to make value u32 and add a spinlock? value is has
>> not 64bit on 64bit systems and it uses only the first 23bits for the
>> size and bit 24+25 for the two flags we have now. So the size should not
>> change on 64bit systems only increase by four byte on 32bit systems.
>> That is without the lock debugging of course.
>>
>> Minchan, Nitin, Sergey do see any reason not to do so?
> 
> that's increased size for every table entry + lock debugging bloat;
> not exactly what zram is trying to do. sounds bad enough.

That size is _only_ increased with lockdep enabled. So if you that much
concerned about size of this struct why not disable lockdep?

> 
> 	-ss
> 
Sebastian