Date: Wed, 12 Feb 2014 02:02:01 +0000 From: "Gumpula, Suresh" <Suresh.Gumpula@netapp.com> To: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: malloc(9) and its alignment Message-ID: <D29CB80EBA4DEA4D91181928AAF51538438EED0A@SACEXCMBX04-PRD.hq.netapp.com>
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Hi,
It appears the malloc(9) returns 8 byte aligned ( UMA_ALIGN_PTR) pointers,=
but in bus_dmamem_alloc we might end up checking for greater alignment
if we take malloc(9) path instead contig_malloc.
Can someone please confirm if malloc(9) returns different alignment pointer=
s ?
bus_dmamem_alloc(bus_dma_tag_t dmat, void** vaddr, int flags,
bus_dmamap_t *mapp)
{
/*
* XXX:
* (dmat->alignment < dmat->maxsize) is just a quick hack; the exac=
t
* alignment guarantees of malloc need to be nailed down, and the
* code below should be rewritten to take that into account.
*
* In the meantime, we'll warn the user if malloc gets it wrong.
*/
if ((dmat->maxsize <=3D PAGE_SIZE) &&
(dmat->alignment < dmat->maxsize) &&
dmat->lowaddr >=3D ptoa((vm_paddr_t)Maxmem)) {
*vaddr =3D malloc(dmat->maxsize, M_DEVBUF, mflags);
} else {
*vaddr =3D contigmalloc(dmat->maxsize, M_DEVBUF, mflags,
0ul, dmat->lowaddr, dmat->alignment? dmat->alignment : =
1ul,
dmat->boundary);
}=20
if (vtophys(*vaddr) & (dmat->alignment - 1)) {
NETAPP_MUTED_PRINTF("bus_dmamem_alloc failed to align memor=
y properly.\n");
Regards,
Suresh
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