From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Tue,  4 Oct 2011 10:13:40 -0400
To: 9fans@9fans.net
Message-ID: <062948585b96427f121f35b27c1f90fe@brasstown.quanstro.net>
In-Reply-To: <cae68b045335522b8d7bfbdf9260bb3b@hamnavoe.com>
References: <cae68b045335522b8d7bfbdf9260bb3b@hamnavoe.com>
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Subject: Re: [9fans] copying fossil filesystem to a bigger disk
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> Is there any experiment I can do (not involving a crowbar and a
> microscope) to find out the real physical sector size?  Bigger
> transfers get more of the bandwidth, but then a smaller proportion
> of the transfer needs read/modify/write.  I could do random addressing
> but then I would expect seek time to dominate.
>
> Not that it matters (my drive works fine), but I'm curious!

i think the attached program ought to work.  here are some local
results.  no 4k-sector drives.  sorry.  if this doesn't work, especially for
writing, it's probablly a caching effect.  you may need to run till
the cache fills up (64mb or so) and then start timing.

iosz	r (s)	riops	w	wiops	model
512	12.227	81.78	5.531	180.78	Hitachi HUA721050KLA330
4096	12.363	80.88	5.649	176.99	Hitachi HUA721050KLA330
512	5.957	167.85	2.636	379.26	SEAGATE ST373455SS (sas)
4096	5.946	168.15	2.665	375.19	SEAGATE ST373455SS (sas)
512	0.181	5494.54	0.168	5941.86	SSDSA2SH064G1GC INTEL (ssd)
4096	0.317	3150.64	0.213	4689.26	SSDSA2SH064G1GC INTEL (ssd)

as already known, none of these appear to have any sector size wierdness.

surprising, considering the intel ssd is attached to a openrd!

- erik
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#include <u.h>
#include <libc.h>

enum {
	Ios	= 1000,		/* number of ios / test */
	Nanoi	= 1000000000,	/* 1/nano */
	Microi	= 1000000,
};

enum {
	Read	= 1<<0,
	Write	= 1<<1,
};

static int otab[4] = {
[Read]		OREAD,
[Write]		OWRITE,
[Read|Write]	ORDWR,
};

static char *rwtab[4] = {
[Read]		"read",
[Write]		"write",
[Read|Write]	"rdwr",
};

void
rio(int fd, uvlong byte0, uvlong bytes, uint ss, int rw)
{
	char *buf;
	int i;
	uvlong maxlba, lba, t, x;
	long (*io)(int, void*, long, vlong);

	maxlba = (bytes - byte0) / ss;
	if(rw == Read)
		io = pread;
	else if(rw == Write)
		io = pwrite;
	else{
		io = nil;		/* compiler noise */
		sysfatal("not prepared to mix read/write yet");
	}

	buf = malloc(ss);
	if(buf == nil)
		sysfatal("malloc");

	srand(nsec());
	t = -nsec();
	for(i = 0; i < Ios; i++){
		lba = frand()*maxlba;	/* awful.  no vlnrand() */
		io(fd, buf, ss, byte0 + lba*ss);
	}
	t += nsec();
	free(buf);

	print("%s %lld.%03lld\n", rwtab[rw], t/Nanoi, (t%Nanoi)/Microi);
	x = (uvlong)Ios*(uvlong)Nanoi*100;
	x /= t;
	print("%lld.%02lld iops\n", x/100, (x%100));
}

void
usage(void)
{
	fprint(2, "usage: randomio [-rw] [-o offset] [-s sectorsz] [file ...]\n");
	exits("usage");
}

void
main(int argc, char **argv)
{
	int i, byte0, fd, rw, ss;
	uvlong bytes;
	Dir *d;

	rw = 0;
	ss = 512;
	byte0 = 0;
	ARGBEGIN{
	case 'r':
		rw |= Read;
		break;
	case 'w':
		rw |= Write;
		break;
	case 'o':
		byte0 = atoi(EARGF(usage()));
		break;
	case 's':
		ss = atoi(EARGF(usage()));
		break;
	default:
		usage();
	}ARGEND;

	if(rw == 0)
		rw = Read;

	for(i = 0; i < argc; i++){
		d = dirstat(argv[i]);
		if(d == nil)
			sysfatal("dirstat: %r");
		bytes = d->length;
		free(d);

		fd = open(argv[i], otab[rw]);
		if(fd == -1)
			sysfatal("open: %r");

		if(rw & Read)
			rio(fd, byte0, bytes, ss, Read);
		if(rw & Write)
			rio(fd, byte0, bytes, ss, Write);
		close(fd);
	}
	exits("");
}
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