On 12/11/18 08:09, Otto Moerbeek wrote:
> On Mon, Dec 10, 2018 at 11:44:47AM +0100, Otto Moerbeek wrote:
>
>> On Mon, Dec 10, 2018 at 08:30:10AM +0100, Otto Moerbeek wrote:
>>
>> > Hi,
>> >
>> > the bootloader uses a very simple allocator for dynamic memory. It
>> > maintains a list of free allocations. If it needs a block, it searches
>> > the freelist and returns the smallest allocation that fits.
>> >
>> > Allocation patterns like this (starting with an empty freelist)
>> >
>> > alloc(big)
>> > free(big)
>> > alloc(small)
>> >
>> > will assigned a big block for the small allocation, wasting most
>> > memory. The allocator does not split up this block. After this, a new
>> > big allocation will grow the heap with the big amount. This diff
>> > changes the strategy by not re-using a block from the free list if
>> > half the space or more would be wasted. Instead, it grows the heap by
>> > the requested amount.
>> >
>> > This make it possible for me to boot using a root fs with a large
>> > blocksize. There have been several reports of large roots not working
>> > (the bootloader allocates memory based om the blocksize of the file
>> > system, and by default larger filesystems use larger blocks).
>> >
>> > How to test
>> > ===========
>> >
>> > Apply diff and do a full build including building release. After that,
>> > either upgrade using your newly built cd64.iso, bsd.rd or other
>> > mechanism or do a full install. Test that you can boot afterwards.
>> >
>> > This needs to be tested on various platforms, both will small and big
>> > (> 600G) root filesystems. Yes, this is tedious, but we want large
>> > coverage of different cases.
>> >
>> > -Otto
>>
>> As it turns out by my own testing, on amd64 root filssytems using 32k
>> blocks now work fine, but 64k fs blocks still hit a ceiling. This
>> corresponds to > 512G disks if you use the defaults.
>>
>> -Otto
>>
>
> New diff that also works on root filesystems > 500G. It avoid using a
> large bouncebuffer by reding large buffers in a loop instead of one go.
>
> -Otto
You are my hero.
Seems it is possible to hose a system by making a 32k block size on a
system with a root file system of only 500MB. I really don't know how I
did this, much less why, but it's been causing me reboot problems for
over a year now.
Upgraded to today's snap, problem solved.
Nick.
/home/nick $ dmesg|head
OpenBSD 6.4-current (GENERIC.MP) #510: Thu Dec 13 06:20:42 MST 2018
dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> p m
OpenBSD area: 64-2000397735; size: 976756.7M; free: 859532.4M
# size offset fstype [fsize bsize cpg]
a: 502.0M 64 4.2BSD 4096 32768 1 # / # wtf?
b: 20473.5M 1048578560 swap #
c: 976762.3M 0 unused
d: 10244.6M 1090508288 4.2BSD 2048 16384 1 # /usr
e: 4094.7M 1111489152 4.2BSD 2048 16384 1 # /tmp
f: 10236.7M 1119875072 4.2BSD 2048 16384 1 # /var
g: 20473.5M 1161804704 4.2BSD 2048 16384 1 # /repo
h: 10236.7M 1140839904 4.2BSD 2048 16384 1 # /home
i: 7.8M 1203734368 4.2BSD 2048 16384 1 #
j: 40954.8M 1203750432 4.2BSD 2048 16384 1
> Index: arch/amd64/stand/libsa/biosdev.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/amd64/stand/libsa/biosdev.c,v
> retrieving revision 1.32
> diff -u -p -r1.32 biosdev.c
> --- arch/amd64/stand/libsa/biosdev.c 10 Aug 2018 16:41:35 -0000 1.32
> +++ arch/amd64/stand/libsa/biosdev.c 11 Dec 2018 13:00:02 -0000
> @@ -340,11 +340,26 @@ biosd_io(int rw, bios_diskinfo_t *bd, u_
> return error;
> }
>
> +#define MAXSECTS 32
> +
> int
> biosd_diskio(int rw, struct diskinfo *dip, u_int off, int nsect, void *buf)
> {
> - return biosd_io(rw, &dip->bios_info, off, nsect, buf);
> + int i, n, ret;
> +
> + /*
> + * Avoid doing too large reads, the bounce buffer used by biosd_io()
> + * might run us out-of-mem.
> + */
> + for (i = 0, ret = 0; ret == 0 && nsect > 0;
> + i += MAXSECTS, nsect -= MAXSECTS) {
> + n = nsect >= MAXSECTS ? MAXSECTS : nsect;
> + ret = biosd_io(rw, &dip->bios_info, off + i, n,
> + buf + i * DEV_BSIZE);
> + }
> + return ret;
> }
> +
> /*
> * Try to read the bsd label on the given BIOS device.
> */
> @@ -715,7 +730,6 @@ biosstrategy(void *devdata, int rw, dadd
> size_t *rsize)
> {
> struct diskinfo *dip = (struct diskinfo *)devdata;
> - bios_diskinfo_t *bd = &dip->bios_info;
> u_int8_t error = 0;
> size_t nsect;
>
> @@ -732,7 +746,7 @@ biosstrategy(void *devdata, int rw, dadd
> if (blk < 0)
> error = EINVAL;
> else
> - error = biosd_io(rw, bd, blk, nsect, buf);
> + error = biosd_diskio(rw, dip, blk, nsect, buf);
>
> #ifdef BIOS_DEBUG
> if (debug) {
> Index: arch/i386/stand/libsa/biosdev.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/i386/stand/libsa/biosdev.c,v
> retrieving revision 1.98
> diff -u -p -r1.98 biosdev.c
> --- arch/i386/stand/libsa/biosdev.c 6 Sep 2018 11:50:54 -0000 1.98
> +++ arch/i386/stand/libsa/biosdev.c 11 Dec 2018 13:00:02 -0000
> @@ -341,11 +341,26 @@ biosd_io(int rw, bios_diskinfo_t *bd, u_
> return error;
> }
>
> +#define MAXSECTS 32
> +
> int
> biosd_diskio(int rw, struct diskinfo *dip, u_int off, int nsect, void *buf)
> {
> - return biosd_io(rw, &dip->bios_info, off, nsect, buf);
> + int i, n, ret;
> +
> + /*
> + * Avoid doing too large reads, the bounce buffer used by biosd_io()
> + * might run us out-of-mem.
> + */
> + for (i = 0, ret = 0; ret == 0 && nsect > 0;
> + i += MAXSECTS, nsect -= MAXSECTS) {
> + n = nsect >= MAXSECTS ? MAXSECTS : nsect;
> + ret = biosd_io(rw, &dip->bios_info, off + i, n,
> + buf + i * DEV_BSIZE);
> + }
> + return ret;
> }
> +
> /*
> * Try to read the bsd label on the given BIOS device.
> */
> @@ -716,7 +731,6 @@ biosstrategy(void *devdata, int rw, dadd
> size_t *rsize)
> {
> struct diskinfo *dip = (struct diskinfo *)devdata;
> - bios_diskinfo_t *bd = &dip->bios_info;
> u_int8_t error = 0;
> size_t nsect;
>
> @@ -733,7 +747,7 @@ biosstrategy(void *devdata, int rw, dadd
> if (blk < 0)
> error = EINVAL;
> else
> - error = biosd_io(rw, bd, blk, nsect, buf);
> + error = biosd_diskio(rw, dip, blk, nsect, buf);
>
> #ifdef BIOS_DEBUG
> if (debug) {
> Index: lib/libsa/alloc.c
> ===================================================================
> RCS file: /cvs/src/sys/lib/libsa/alloc.c,v
> retrieving revision 1.12
> diff -u -p -r1.12 alloc.c
> --- lib/libsa/alloc.c 14 Mar 2016 23:08:06 -0000 1.12
> +++ lib/libsa/alloc.c 11 Dec 2018 13:00:03 -0000
> @@ -169,7 +169,7 @@ alloc(unsigned int size)
> }
>
> /* no match in freelist if bestsize unchanged */
> - failed = (bestsize == 0xffffffff);
> + failed = (bestsize == 0xffffffff || bestsize >= size * 2);
> #endif
>
> if (failed) { /* nothing found */
>
