Re: [Xen-devel] [PATCH] libxl: remove LIBXL_MAXMEM_CONSTANT

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 25 Feb 2015, Don Slutz wrote:
> On 02/25/15 10:07, Stefano Stabellini wrote:
> > LIBXL_MAXMEM_CONSTANT is used to increase the maxmem setting for a
> > domain by a constant amount. As it is not clear the reason why we should
> > be doing this, remove the constant.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > CC: mlatimer@xxxxxxxx
> > CC: ian.campbell@xxxxxxxxxx
> > ---
> 
> I think that some sort of link to commit 901230f in QEMU:
> 
> ----
> commit 901230fd8ce053cc21312a2eca2f3ba9f1d103f2
> Author: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Date:   Wed Dec 3 08:15:19 2014 -0500
> 
>     xen-hvm: increase maxmem before calling xc_domain_populate_physmap
> 
>     Increase maxmem before calling xc_domain_populate_physmap_exact to
>     avoid the risk of running out of guest memory. This way we can also
>     avoid complex memory calculations in libxl at domain construction
>     time.
> 
>     This patch fixes an abort() when assigning more than 4 NICs to a VM.
> 
>     upstream-commit-id: c1d322e6048796296555dd36fdd102d7fa2f50bf
> 
>     Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>     Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> ----
> 
> Because after this patch and without a "correct" QEMU, the number of
> e1000 NICs a guest can use is less then 4.

That is true, in fact is not even a single emulated NIC in my tests.
I can either ask for a backport of
c1d322e6048796296555dd36fdd102d7fa2f50bf "xen-hvm: increase maxmem
before calling xc_domain_populate_physmap" to all QEMU stable branches,
or we just have to keep this around for now and maybe just add a comment
on why it is needed.


> >  tools/libxl/libxl.c          |    9 ++++-----
> >  tools/libxl/libxl_dom.c      |    3 +--
> >  tools/libxl/libxl_internal.h |    1 -
> >  3 files changed, 5 insertions(+), 8 deletions(-)
> > 
> > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> > index b9a1941..9556a92 100644
> > --- a/tools/libxl/libxl.c
> > +++ b/tools/libxl/libxl.c
> > @@ -4572,11 +4572,11 @@ int libxl_domain_setmaxmem(libxl_ctx *ctx, uint32_t 
> > domid, uint32_t max_memkb)
> >          LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "memory_static_max must be 
> > greater than or or equal to memory_dynamic_max\n");
> >          goto out;
> >      }
> > -    rc = xc_domain_setmaxmem(ctx->xch, domid, max_memkb + 
> > LIBXL_MAXMEM_CONSTANT);
> > +    rc = xc_domain_setmaxmem(ctx->xch, domid, max_memkb);
> >      if (rc != 0) {
> >          LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
> >                  "xc_domain_setmaxmem domid=%d memkb=%d failed "
> > -                "rc=%d\n", domid, max_memkb + LIBXL_MAXMEM_CONSTANT, rc);
> > +                "rc=%d\n", domid, max_memkb, rc);
> >          goto out;
> >      }
> >  
> > @@ -4796,12 +4796,11 @@ retry_transaction:
> >  
> >      if (enforce) {
> >          memorykb = new_target_memkb + videoram;
> > -        rc = xc_domain_setmaxmem(ctx->xch, domid, memorykb +
> > -                LIBXL_MAXMEM_CONSTANT);
> > +        rc = xc_domain_setmaxmem(ctx->xch, domid, memorykb);
> >          if (rc != 0) {
> >              LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
> >                      "xc_domain_setmaxmem domid=%d memkb=%d failed "
> > -                    "rc=%d\n", domid, memorykb + LIBXL_MAXMEM_CONSTANT, 
> > rc);
> > +                    "rc=%d\n", domid, memorykb, rc);
> >              abort_transaction = 1;
> >              goto out;
> >          }
> > diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
> > index a16d4a1..923ba5c 100644
> > --- a/tools/libxl/libxl_dom.c
> > +++ b/tools/libxl/libxl_dom.c
> > @@ -408,8 +408,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
> >          }
> >      }
> >  
> > -    if (xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb +
> > -        LIBXL_MAXMEM_CONSTANT) < 0) {
> > +    if (xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb) < 0) {
> >          LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "Couldn't set max memory");
> >          return ERROR_FAIL;
> >      }
> > diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> > index 934465a..d5c5b68 100644
> > --- a/tools/libxl/libxl_internal.h
> > +++ b/tools/libxl/libxl_internal.h
> > @@ -89,7 +89,6 @@
> >  #define LIBXL_QEMU_BODGE_TIMEOUT 2
> >  #define LIBXL_XENCONSOLE_LIMIT 1048576
> >  #define LIBXL_XENCONSOLE_PROTOCOL "vt100"
> > -#define LIBXL_MAXMEM_CONSTANT 1024
> >  #define LIBXL_PV_EXTRA_MEMORY 1024
> >  #define LIBXL_HVM_EXTRA_MEMORY 2048
> >  #define LIBXL_MIN_DOM0_MEM (128*1024)
> > 
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel