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Dejun Luo

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Published work

21 published item(s)

preprint2026arXiv

KVServe: Service-Aware KV Cache Compression for Communication-Efficient Disaggregated LLM Serving

LLMs are widely adopted in production, pushing inference systems to their limits. Disaggregated LLM serving (e.g., PD separation and KV state disaggregation) improves scalability and cost efficiency, but it also turns KV into an explicit payload crossing network and storage boundaries, making KV a dominant end-to-end bottleneck. Existing KV compression are typically static runtime configurations, despite production service context varies over time in workload mix, bandwidth, and SLO/quality budgets. As a result, a fixed choice can be suboptimal or even increase latency. We present \emph{KVServe}, the first service-aware and adaptive KV communication compression framework for disaggregated LLM serving: KVServe (1) unifies KV compression into a modular strategy space with new components and cross-method recomposition; (2) introduces Bayesian Profiling Engine that efficiently searches this space and distills a 3D Pareto candidate set, reducing $50\times$ offline search overhead; and (3) deploys a Service-Aware Online Controller that combines an analytical latency model with a lightweight bandit to select profiles under constraints and correct offline-to-online mismatch. Integrated into vLLM and evaluated across datasets, models, GPUs and networks, KVServe achieves up to $9.13\times$ JCT speedup in PD-separated serving and up to $32.8\times$ TTFT reduction in KV-disaggregated serving.

preprint2026arXiv

Structure preservation and emergent dissipation in stochastic wave equations with transport noise

We study nonlinear wave equations perturbed by transport noise acting either on the displacement or on the velocity. Such noise models random advection and, under suitable scaling of space covariance, may generate an effective dissipative term. We establish well-posedness in both cases and analyse the associated scaling limits. When the noise acts on the displacement, the system preserves its original structure and converges to the deterministic nonlinear wave equation, whereas if it acts on the velocity, the rescaled dynamics produce an additional Laplacian damping term, leading to a stochastic derivation of a Westervelt-type acoustic model.

preprint2019arXiv

Energy conditional measures and 2D turbulence

We show that the invariant measure of point vortices, when conditioning the Hamiltonian to a finite interval, converges weakly to the enstrophy measure by conditioning the renormalized energy to the same interval. We also prove the existence of solutions to 2D Euler equations having the energy conditional measure as invariant measure. Some heuristic discussions and numerical simulations are presented in the last section.

preprint2016arXiv

Exponential Convergence in $L^p$-Wasserstein Distance for Diffusion Processes without Uniformly Dissipative Drift

By adopting the coupling by reflection and choosing an auxiliary function which is convex near infinity, we establish the exponential convergence of diffusion semigroups $(P_t)_{t\ge0}$ with respect to the standard $L^p$-Wasserstein distance for all $p\in[1,\infty)$. In particular, we show that for the Itô stochastic differential equation $$\d X_t=\d B_t+b(X_t)\,\d t,$$ if the drift term $b$ satisfies that for any $x,y\in\R^d$, $$\langle b(x)-b(y),x-y\rangle\le \begin{cases} K_1|x-y|^2,& |x-y|\le L; -K_2|x-y|^2,& |x-y|> L \end{cases}$$ holds with some positive constants $K_1$, $K_2$ and $L>0$, then there is a constant $λ:=λ(K_1,K_2,L)>0$ such that for all $p\in[1,\infty)$, $t>0$ and $x,y\in\R^d$, $$W_p(δ_x P_t,δ_y P_t)\leq Ce^{-λt/p} \begin{cases} |x-y|^{1/p}, & \mbox{if } |x-y|\le 1; |x-y|, & \mbox{if } |x-y|> 1. \end{cases}$$ where $C:=C(K_1,K_2,L,p)$ is a positive constant. This improves the main result in \cite{Eberle} where the exponential convergence is only proved for the $L^1$-Wasserstein distance.

preprint2015arXiv

A probabilistic proof of the fundamental gap conjecture via the coupling by reflection

Let $Ω\subset\mathbb{R}^n$ be a strictly convex domain with smooth boundary and diameter $D$. The fundamental gap conjecture claims that if $V:\barΩ\to\mathbb{R}$ is convex, then the spectral gap of the Schrödinger operator $-Δ+V$ with Dirichlet boundary condition is greater than $\frac{3π^2}{D^2}$. Using analytic methods, Andrews and Clutterbuck recently proved in [J. Amer. Math. Soc. 24 (2011), no. 3, 899--916] a more general spectral gap comparison theorem which implies this conjecture. In the first part of the current work, we shall give an independent probabilistic proof of their result via the coupling by reflection of the diffusion processes. Moreover, we also present in the second part a simpler probabilistic proof of the original conjecture.

preprint2014arXiv

Harnack Inequalities for SDEs with Multiplicative Noise and Non-regular Drift

The log-Harnack inequality and Harnack inequality with powers for semigroups associated to SDEs with non-degenerate diffusion coefficient and non-regular time-dependent drift coefficient are established, based on the recent papers \cite{Flandoli, Zhang11}. We consider two cases in this work: (1) the drift fulfills the LPS-type integrability, and (2) the drift is uniformly Hölder continuous with respect to the spatial variable. Finally, by using explicit heat kernel estimates for the stable process with drift, the Harnack inequality for the stochastic differential equation driven by symmetric stable process is also proved.

preprint2014arXiv

Quasi-invariance of the stochastic flow associated to Itô's SDE with singular time-dependent drift

In this paper we consider the Itô SDE $$d X_t=d W_t+b(t,X_t)\,d t, \quad X_0=x\in {\mathbb R}^d,$$ where $W_t$ is a $d$-dimensional standard Wiener process and the drift coefficient $b:[0,T]\times{\mathbb R}^d\to{\mathbb R}^d$ belongs to $L^q(0,T;L^p({\mathbb R}^d))$ with $p\geq 2, q>2$ and $\frac dp +\frac 2q<1$. In 2005, Krylov and Röckner \cite{KR05} proved that the above equation has a unique strong solution $X_t$. Recently it was shown by Fedrizzi and Flandoli \cite{FF13b} that the solution $X_t$ is indeed a stochastic flow of homeomorphisms on ${\mathbb R}^d$. We prove in the present work that the Lebesgue measure is quasi-invariant under the flow $X_t$.

preprint2014arXiv

Stochastic Lagrangian flows on the group of volume-preserving homeomorphisms of the spheres

We consider stochastic differential equations on the group of volume-preserving homeomorphisms of the sphere $S^d\,(d\geq 2)$. The diffusion part is given by the divergence free eigenvector fields of the Laplacian acting on $L^2$-vector fields, while the drift is some other divergence free vector field. We show that the equation generates a unique flow of measure-preserving homeomorphisms when the drift has first order Sobolev regularity, and derive a formula for the distance between two Lagrangian flows. We also compute the rotation process of two particles on the sphere $S^2$ when they are close to each other.

preprint2014arXiv

Uniform Hölder Estimates on Semigroups Generated by Non-Local Operators of Variable Order

We consider the non-local operator of variable order as follows $$Lf(x)= \int_{\R^d\setminus\{0\}}\big(f(x+z)-f(x)-\<\nabla f(x),z\> \I_{\{|z|\le 1\}}\big)\frac{n(x,z)}{|z|^{d+α(x)}}\,dz.$$ Under mild conditions on $α(x)$ and $n(x,z)$, we establish the Hölder regularity for the associated semigroups. The proof is based on the probabilistic coupling method, and it successfully applies to both stable-like processes in the sense of Bass and time-change of symmetric stable processes.

preprint2013arXiv

The log-Sobolev inequality for the ground state of a Schrödinger operator on bounded convex domains

We consider the ground state $ϕ_0$ of the Schrödinger operator $L=-Δ+V$ on the bounded convex domain $Ω\subset\R^n$, satisfying the Dirichlet boundary condition. Assume that $V\in C^1(Ω)$ and it admits an even function $\tilde V\in C^1([-D/2,D/2])$ as its modulus of convexity, where $D$ is the diameter of $Ω$. If the first Dirichlet eigenvalue $\tildeλ_0$ of $-\frac{\d^2}{\d t^2}+\tilde V$ on the interval $[-D/2,D/2]$ satisfies $\tildeλ_0>\tilde V(0)$, then the measure $\dμ=ϕ_0 \d x$ satisfies the log-Sobolev inequality on $Ω$ with the constant $\tildeλ_0-\tilde V(0)$. In particular, if $V$ is convex, then the constant is explicitly given by $\frac{π^2}{D^2}$.

preprint2012arXiv

Generalized stochastic flow associated to the Itô SDE with partially Sobolev coefficients and applications

We consider the Itô SDE with partially Sobolev coefficients. Under some suitable conditions, we show the existence, uniqueness and stability of generalized stochastic flows associated to such an equation. As an application, we prove the weak differentiability of the stochastic flow generated by the Itô SDE with Sobolev coefficients.

preprint2010arXiv

A note on Gaussian correlation inequalities for nonsymmetric sets

We consider the Gaussian correlation inequality for nonsymmetric convex sets. More precisely, if $A\subset\mathbb{R}^d$ is convex and the origin $0\in A$, then for any ball $B$ centered at the origin, it holds $γ_d(A\cap B)\geq γ_d(A)γ_d(B)$, where $γ_d$ is the standard Gaussian measure on $\mathbb{R}^d$. This generalizes Proposition 1 in [Arch. Rational Mech. Anal. 161 (2002), 257--269].

preprint2010arXiv

Absolute continuity under flows generated by SDE with measurable drift coefficient

We consider the Itô SDE with non-degenerate diffusion coefficient and measurable drift coefficient. Under the condition that the gradient of the diffusion coefficient and the divergences of the diffusion and drift coefficients are exponentially integrable with respect to the Gaussian measure, we show that the stochastic flow leaves the reference measure absolutely continuous.

preprint2010arXiv

Asymptotic estimates on the time derivative of entropy on a Riemannian manifold

We consider the entropy of the solution to the heat equation on a Riemannian manifold. When the manifold is compact, we provide two estimates on the rate of change of the entropy in terms of the lower bound on the Ricci curvature and the spectral gap respectively. Our explicit computation for the three dimensional hyperbolic space shows that the time derivative of the entropy is asymptotically bounded by two positive constants.

preprint2010arXiv

Quasi-invariant flow generated by Stratonovich SDE with BV drift coefficients

We generalize the results of Ambrosio [Invent. Math. 158 (2004), 227--260] on the existence, uniqueness and stability of regular Lagrangian flows of ordinary differential equations to Stratonovich stochastic differential equations with BV drift coefficients. Then we construct an explicit solution to the corresponding stochastic transport equation in terms of the stochastic flow. The approximate differentiability of the flow is also studied when the drift is a Sobolev vector field.

preprint2010arXiv

Stochastic differential equations with coefficients in Sobolev spaces

We consider Itô SDE $\d X_t=\sum_{j=1}^m A_j(X_t) \d w_t^j + A_0(X_t) \d t$ on $\R^d$. The diffusion coefficients $A_1,..., A_m$ are supposed to be in the Sobolev space $W_\text{loc}^{1,p} (\R^d)$ with $p>d$, and to have linear growth; for the drift coefficient $A_0$, we consider two cases: (i) $A_0$ is continuous whose distributional divergence $δ(A_0)$ w.r.t. the Gaussian measure $γ_d$ exists, (ii) $A_0$ has the Sobolev regularity $W_\text{loc}^{1,p'}$ for some $p'>1$. Assume $\int_{\R^d} \exp\big[λ_0\bigl(|δ(A_0)| + \sum_{j=1}^m (|δ(A_j)|^2 +|\nabla A_j|^2)\bigr)\big] \dγ_d<+\infty$ for some $λ_0>0$, in the case (i), if the pathwise uniqueness of solutions holds, then the push-forward $(X_t)_# γ_d$ admits a density with respect to $γ_d$. In particular, if the coefficients are bounded Lipschitz continuous, then $X_t$ leaves the Lebesgue measure $\Leb_d$ quasi-invariant. In the case (ii), we develop a method used by G. Crippa and C. De Lellis for ODE and implemented by X. Zhang for SDE, to establish the existence and uniqueness of stochastic flow of maps.