linux-kernel - Re: [SUGGESTION]: drop virtual merge accounting in I/O requests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 14 Jul 2008 19:16:17 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	David Miller <davem@...emloft.net>
cc:	andi@...stfloor.org, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org, jens.axboe@...cle.com
Subject: Re: [SUGGESTION]: drop virtual merge accounting in I/O requests

>>>> As you mentioned ESP driver, it declares .sg_tablesize = SG_ALL, so
>>>> BIO_VMERGE_BOUNDARY has no effect on the operation of this driver. Any
>>>> other driver where BIO_VMERGE_BOUNDARY does matter?
>>>
>>> When BIO_VMERGE_BOUNDARY is turned on, requests that would not
>>> otherwise fit into the device's limits, can.
>>
>> Why would someone want to overshoot SG_ALL? ... and, shouldn't the
>> constant be increased then --- instead of making buggy BIO_VMERGE_BOUNDARY
>> expectations?
>
> I'm talking about other devices, not about the ESP, here.

And which ones are those important drivers that need merge accounting?

A100U2W is an old card, I got it for $8.5 in bazaar, it does 38MB/s. This 
virtual merge accounting helps to stuff on average 4 more segments into 
the 32-entry table.

So the question is: to reduce number of requests by 12% on an outdated 
SCSI card, it is sensible to maintain complicated merge accounting logic 
in the core block layer? To me, it doesn't seem sensible.

Mikulas
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/