This is the mail archive of the mailing list for the glibc project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Add TUNABLES to control IFUNC selection and cache sizes

On Thu, Jun 8, 2017 at 10:45 PM, Siddhesh Poyarekar <> wrote:
> On Friday 09 June 2017 01:33 AM, H.J. Lu wrote:
>> The current IFUNC selection is based on microbenchmarks in glibc.  It
>> should give the best performance for most workloads.  But other choices
>> may have better performance for a particular workload or on the hardware
>> which wasn't available at the selection was made.  The environment
>> variable, GLIBC_IFUNC=-xxx,yyy,-zzz...., can be used to enable CPU/ARCH
>> feature yyy, disable CPU/ARCH feature yyy and zzz, where the feature
>> name is case-sensitive and has to match the ones in cpu-features.h.  It
>> can be used by glibc developers to override the IFUNC selection to tune
>> for a new processor or improve performance for a particular workload.
>> It isn't intended for normal end users.
> We have agreed in the past that env_alias is only a compatibility hack
> to allow existing environment variables to be ported into tunables so
> please don't add new ones.  glibc.tune.ifunc should be the only way to
> select ifuncs.
> Siddhesh

Does that mean tunables must be enabled to use it? Will tunables
be enabled by default?


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]