From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 33F27900149 for ; Tue, 4 Oct 2011 15:37:49 -0400 (EDT) Received: from /spool/local by us.ibm.com with XMail ESMTP for from ; Tue, 4 Oct 2011 15:36:48 -0400 Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay03.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p94JZm0f110624 for ; Tue, 4 Oct 2011 15:35:48 -0400 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p94JZlud004522 for ; Tue, 4 Oct 2011 16:35:48 -0300 Subject: Re: [RFCv3][PATCH 1/4] replace string_get_size() arrays From: Dave Hansen In-Reply-To: <1317497626.22613.1.camel@Joe-Laptop> References: <20111001000856.DD623081@kernel> <1317497626.22613.1.camel@Joe-Laptop> Content-Type: text/plain; charset="UTF-8" Date: Tue, 04 Oct 2011 12:35:42 -0700 Message-ID: <1317756942.7842.38.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joe Perches Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, rientjes@google.com, James.Bottomley@HansenPartnership.com, hpa@zytor.com On Sat, 2011-10-01 at 12:33 -0700, Joe Perches wrote: > On Fri, 2011-09-30 at 17:08 -0700, Dave Hansen wrote: > > Instead of explicitly storing the entire string for each > > possible units, just store the thing that varies: the > > first character. > > trivia I'm not sure what you mean by that. > > diff -puN lib/string_helpers.c~string_get_size-pow2 lib/string_helpers.c > > --- linux-2.6.git/lib/string_helpers.c~string_get_size-pow2 2011-09-30 16:50:31.628981352 -0700 > > +++ linux-2.6.git-dave/lib/string_helpers.c 2011-09-30 17:04:02.211607364 -0700 > > @@ -8,6 +8,23 @@ > > #include > > #include > > > > +static const char byte_units[] = "_KMGTPEZY"; > > u64 could be up to ~1.8**19 decimal > zetta and yotta are not possible or necessary. > u128 maybe someday, but then other changes > would be necessary too. Right, but we're only handling u64. > > +static char *__units_str(enum string_size_units unit, char *buf, int index) > > +{ > > + int place = 0; > > + > > + /* index=0 is plain 'B' with no other unit */ > > + if (index) { > > + buf[place++] = byte_units[index]; > > index is unbounded (doesn't matter currently, it will for u128) It's bound by the division or the log2 at least. You do have to know what you're passing in to __units_str, just like you had to know what you were indexing with in to units_2[] and units_10[]. Is there something else you'd like to see done here? We can bounds-check index, but that seems a bit unnecessary since it's static and the two callers are visible on the same page of code. > > @@ -23,26 +40,19 @@ > > int string_get_size(u64 size, const enum string_size_units units, > > char *buf, int len) > [] > > const unsigned int divisor[] = { > > [STRING_UNITS_10] = 1000, > > [STRING_UNITS_2] = 1024, > > }; > > static const or it might be better to use > unsigned int divisor = (string_size_units == STRING_UNITS_2) ? 1024 : 1000; > as that would make the code clearer in a > couple of uses of divisor[] later. > > > @@ -61,7 +71,7 @@ int string_get_size(u64 size, const enum > > } > > > > snprintf(buf, len, "%lld%s %s", (unsigned long long)size, > > %llu These two are about existing code, and not really necessary for this set. They'd make good follow-on patches, though. -- Dave -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org