linux-kernel - Re: [RFC PATCH v2] iov_iter: Convert iterate*() to inline funcs

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Date:   Mon, 14 Aug 2023 22:40:08 +0100
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com, Alexander Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        Christian Brauner <christian@...uner.io>,
        Matthew Wilcox <willy@...radead.org>, jlayton@...nel.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] iov_iter: Convert iterate*() to inline funcs


>         _copy_from_iter                          inc 0x36e -> 0x395 +0x27

Here a disassembly of _copy_from_iter() from unpatched and patched, marked up for
the different iterator-type branches.  To summarise:

		UNPATCHED	PATCHED
		START	LEN	START	LEN
		=======	=======	=======	=======
Prologue	0	77	0	76
UBUF		77	36	76	36
IOVEC		113	148	112	105
BVEC		261	159	217	163
KVEC		420	125	380	116
XARRAY		545	286	496	374
DISCARD/Epi	831	42	870	42
Return		873	-	912	-


The overall change in the entire file, according to size, is:
   19855     744       0   20599    5077 build3/lib/iov_iter.o -- before
   19739     864       0   20603    507b build3/lib/iov_iter.o -- after

David


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